POLL: Keep tbi or go back to carb

[crispyboy]

OK friends heres the deal. Old Steve is pretty much out of ideas on what to do next with my Howell System. I have worked closely with the programmer at Howell and we have gone through 5 chips. I have what looks pretty close on the BLM's. I have tried a different o2 sensor, IAC, ECU, checked the fuel pressure, map sensor.........
Here's the twist: Cannot get a satisfactory idle out of the engine. Idle is variable, not smooth and drops down about 200 rpm when you put it in gear so the engine almost stalls.
At this point I'm just about ready to throw in the towel. Let me know what you would do:

Trailer the Gw to Howell and pay them to work on it.
Sell the Howell system and try a different one.
Go back to a carburator.

[82Waggy]

Sounds like a simple vacuum leak problem to me. Intake gaskets?

[crispyboy]

Vacuum leak - I have resealed the tbi and adapter. The intake I have is a used Edelbrock Performer. Can these things warp? If it was an internal leak is it possible that I would be burning oil?

[82Waggy]

Yes, intakes can warp - especially if removed when hot. It is also possible that it never fit correctly in the first place due to milling of heads or block decks. Aftermarket intakes sometimes sit too high or low as cast, even if no milling was done to the engine, and mating surfaces are sometimes not parallel to the heads.

Yes, if the intake gasket/valley pan is leaking around the intake ports it can pull oil from the valley into the cylinder(s). Any mis-match as described above can also result in a lack of seal at the gaskets around one or more intake runners.

[82Waggy]

Also, note that leakage at the gaskets can, and usually does, result in unstable idle conditions like you have described, with a significant lack of low end power and a generally lean condition overall. Sometimes this type of leak will seal up after the engine gets warm - making it difficult to track down.

[Mr Fast Bucks]

I have is a used Edelbrock Performer.

Just checking....

Did you install this yourself?

My son and I installed this manifold on his Commando w/360. There are some very specific instructions with the manifold and if you do not follow them your in for some trouble....We had some confusion on this one because he ordered it from Jeggs and it came with gaskets - the type Edelbrock says not to use :confused: According to the instructions you are supposed to use the stock gasket and ditch the end pieces....

Did it run Ok with the carb?

Here are the instructions for the manifold (assuming this is the one you used)
http://www.edelbrock.com/automotive_new/misc/tech_center/install/2000/2131.pdf

[crispyboy]

I installed the intake while the engine was on the stand. One of the possible issues is that I do not know the entire history of the engine. I purchased it from a board member who also did not need the engine. I have papers on the engine from the rebuild shop - no real details on the engine rebuild so I am assuming that it was a standard rebuild.

[82Waggy]

Some shops have a smoke system they can use to pressurize your entire vacuum system, including the manifold, and spot the leaks.

[JeepinPete]

Have you put a vacuum gauge on it? What is it reading, and is it steady? If the vacuum is not steady, it will drive the computer nuts. The MAP sensor is probably the most important sensor of the bunch...

[crispyboy]

vacuum is a steady 15 inches at idle with an RV cam (edelbrock performer)

[FSJ Guy]

Since Howell is in Michigan, trailering is kinda out of the question....

Did you REPLACE the MAP sensor? I've found that mine works pretty well with other sensors disconnected EXCEPT for the MAP. It gives a rough idle without it plugged in or with the MAP not hooked up to manifold vac. It IS hooked up to manifold vac, right? <g>

Does the vac pressure vary according to RPM while idling?

Another thing to consider: Have you run the engine with a carb before? It sounds like this engine has a bit of unknown history and this is the first time you're firing it up after doing some work in it, yes?

[crispyboy]

Map sensor is hooked up to specific port on the back of the throttle body. I have tried the map sensor off of my truck and there is no change in idle quality.
As far as the history of this motor goes - I changed the cam in the motor before I installed it. I did this for two reasons. I wanted to make sure I had an RV type cam in the motor - the engine receipts did not show the specific cam, just that it was replaced. The second reason is that I wanted to have a chip burned specifically for this cam. I spoke with the tech at howell yesterday and he believes that I need to keep working with the base idle and that the ecu needs more time to learn. I have burned up a lot of gas and I'm still not satisfied.
Before I installed the tbi system I ran the engine on a carburator just long enough for cam break-in. I did not take the time to dial it in since I was taking it off anyway. In hindsight this was a mistake - should have made the thing run properly before taking it off. I guess I figured since I had such good luck with installing the tbi on my J20 that this would be a piece of cake.
At this point I think my next course of action is going to be removing the intake manifold and finding out if it is warped/cracked since this seems to be the only thing I have not gone over as of yet:(

[pb]

What is the idle set at in the bin? What are the IAC kickdown steps set at? Also what is the stall saver cut in and out values? If you have a bin and datalog I can look at it for you and see if it is something in the programming.

[crispyboy]

I do not have a bin file. (Maybe I do and don't know it.)
The tech at Howell told me the idle was set at the standard 750 rpm and the steps were the same as their standard chip.
I have equipment at my home that I purchased awhile back from customefis to burn chips and an ecu with the flash chip but I'll be ****ed if I could ever figure out how to work it. (I'll probably sell it one of these days). I am computer illiterate when it comes to working with the chips - this is why I have pay somebody. I have tried to read and figure it out but.......
As for a data capture I was able to save the text file and upload as a pdf. Sorry I had to change it but the space constriaints only allow the upload of small file to ifsja server.
3998

[backpack09]

Did you REPLACE the MAP sensor? I've found that mine works pretty well with other sensors disconnected EXCEPT for the MAP. It gives a rough idle without it plugged in or with the MAP not hooked up to manifold vac. It IS hooked up to manifold vac, right?

Did you try replacing the MAP.

If it made no difference if it was connected or not, I would be suspicious of it.

[BigRedChief]

It sounds like a vacuum issue to me too. Are all your unused ports on the TBI plugged? How about any on the manifold? Do you have an EGR manifold? Is the EGR enabled? Make sure it isn't leaking. I have a Summit Performer copy cam in a 180,000 mile Chevy 350 that pulls more vacuum than you're seeing at idle.

Make sure your IAC is working and moving. I pulled an old one that I thought was dead and replaced it with a new one only to find out that one didn't move either. It turned out there was an intermittent contact issue going on in the plug.

I had another problem that acted a lot like a vacuum leak too. My injectors were not the correct size. They were so small that the engine ran very lean, as if it was taking in a huge amount of excess air. I finally got it to idle okay with those injectors but it would stall as soon as I put it in gear. What injectors do you have? There should be a set of letters/numbers on the top where you can see them. I'd have to look up what the correct ones are again. What is your fuel pressure anyway? If it's a GM based system it's easy to bump up the pressure to compensate for slightly smaller injectors. Make sure you've covered all the other bases before doing that though.

[letank]

interesting challenge here!

15mmHg is a bit on the low end.... seems like you are at sea level. 18 should be more likely

Are you sure that you have an RV cam.... i know that you pull it out of the box.... but items can be boxed improperly, therefore explaining the low vacuum, unless RV cams give you a lower vacuum, i am sure other will give us some light.

next would be to do a compression check, i have seen good vacuum w major headgasket leak.....

Are you up to power at higher rpm

and for the non EFI guys here, droping rpm when putting in gear is normal for the carb people w the slush box.... may be your transmission has some issues... this is what i have after a few days.... as the pump seems to empty.... even if i gas.... it will stumble, unless i wait 1 min in neutral

[YellowJeep]

The motor should see the load of you putting it in gear and try to bump the idle up via the IAC. Have you tested/replaced this? Any way you can get a scan tool or a datalogger on this setup and post the results? It would be helpful to see what the MAP sensor is actually reading and what if anything the IAC is doing. It might be maxed out (open) trying to keep the motor running.

Regardles....keep the TBI and just keep working on the problem.

[crispyboy]

I traded the MAP sensor and IAC with the ones that are on my J20, this is how I know they were working parts.
TBI ports - all are plugged except for the manifold vacuum port going to the distributer. I have no vacuum going to the EGR or emissions. There is no air being pumped into the manifolds.
Compression check - cylinders range from 137 to 145 psi.
Fuel pressure is a constant 13 lbs IIRC.

BigRedChief - How did you figure out that the IAC connector was faulty? If you find the injector numbers please post them.

[BigRedChief]

I went back and forth several times trying a few different things. I think I finally realized the IAC connector was at fault when I put the new IAC motor in and tried resetting it. It wouldn't move. You can look in the IAC hole and see it or you might be able to stick your finger down there and feel it move. Anyway, mine didn't. I wiggled the wires around and suddenly saw movement one time.

The 55lb/hr injectors (for GM 350ci engine) should have the number 5206 on them.

[Ralph Rogers]

Timing? Cam and ign.
Ralph

[jaber]

What about vac lines to the trans? If it drops when put in gear, could it be the trans mod or line to it?

When I put mine together, I had like 50 something in vac, turned out the shop that vated my intake never put the inspection plate on the bottom of the intake.

[shackwrrr]

hook the map sensor up to the manifold instead of the TB if there is no diff between on and off then that would be the problem. that port might be a spark port where theres no vac at idle and some vac just above idle. put the vac guage on that port and see what it reads. if nothing at idle then theres your prob hook it up to the fitting where the booster hooks up to there should be some smaller lines you can tap into

[Gadzooks2]

13 PSI fuel pressure with Fuel injection?
Is that right? I always though fuel injectors needed 50 and up depending on application.

Also, Everyone asks about vacuum leaks, did you spray everyplace it could leak with starting fluid or carb cleaner to see if the idle changes?

Good luck, with the troubleshooting, but I would keep trying to get the injection working. After years of tuning and fixing carbs, I hate'm :banghead:

[crispyboy]

GM tbi systems run on low fuel pressure. I believe the Ford systems run on the high pressure.

I pulled the intake manifold yesterday and I'm going to have it checked out. I may have friend come over when I put it back together who has assembled many engines.

[DieselSJ]

The 13 is about right for a GM TBI. I looked at your log and the thing is swinging from way rich to way lean and the IAC isn't doing much at all. With that wild swing in RPM, the IAC should be all over the place to correct it. I can see where the IAC is open when cold and it continues to close and bring the idle down as the engine warms, but it is doing nothing to try to stabilize the idle.

Shackwrrr has a good suggestion about reading from the manifold for the MAP.

If I had to venture a guess, I'd say that the injectors are a different size that what is programmed into the chip. That can certainly cause idle problems and it is easy to check. Post up the part numbers off the top of the injectors, or just tell me what colors are painted on them and I will tell you what flow rate they are. Then you can verify with Howell that they have it set right in their programming.

Also, make sure you don't have any exhaust leaks - those can throw off the reading at the O2 sensor. While we are talking about the O2 sensor, how far is it mounted away from the engine? More than about 12 inches from the head and you should be running a heated sensor.

One other question...do you have a smog pump? If so, injecting that air into the exhaust manifolds will really mess with the O2 readings.

Hang in there - you will find the problem.

[DieselSJ]

I have been reading through your log a little more. The O2 reading is always rich - it is never going lean according to the O2. It is starting out about 13:1 or so, which is good for a cold idle, but then it just goes whacko and I see it dropping to 12:1, 10:1, 8:1 and it looks like there are a few times when it is hitting like 1:1. But it is NEVER going lean, even with the wild adjustments that the computer is trying to make. I see the computer dropping the BLM to 123, which means it is pulling fuel out, yet you are still way rich.

Are you sure you don't have any plug wires crossed? Valve sticking open? Bad spark plug? Weak coil?

[Bill USN-1]

Not sure where you are at with this but I recognize some of the others here that frequent my FI forum.

There is a lot of people trying to help but some of the info is a little off.

A few basics.

Stoick is 14.7AFR and 128 on the BLM
If the mixture is lean then the number goes up meaning the ECM is adding fuel.
If the AFR is rich then the number is low and the ECM removes fuel.

138 lean
118 rich

Now the O2 swinging up and down is normal for closed loop. That's how the ECM maintains 14.7.

The idle fluctuation or lean roll sometimes occurs. Extreme is normally from a larger cam and trying to idle in closed loop. The valve overlap and raw fuel will play havoc with the O2 readings.


The proper port for the MAP is between the fuel lines.

Now your log indicates that your TPS is set too high at 3.6%
It should be .54 volts or 0%

When you finally get it back together after removing the intake...if it still runs the same then try disconnecting the O2 sensor and see if it helps after it is warmed up.

I also recommend doing the initial setup procedures in the FI forum on the www.Binderbulletin.org (http://www.Binderbulletin.org) where I reside.

I strongly urge all interested in FI to start with the FAQ's at the top of the forum there.

I do not claim to be a self appointed know it all or guru or anything other then a guy who plays with GM FI and have documented what I have learned and try to pass it on.

Good luck

[chr1s]

I do not claim to be a self appointed know it all or guru or anything other then a guy who plays with GM FI and have documented what I have learned and try to pass it on.

Good luck

yep :thumbsup:
Ive gotten tons of info there when troublshooting and tuining my TBI set up.

[LaJ10]

Ditto the site and Bill are both great

[chakaD460]

Not to hijack, but how do you get to the FI site?

I keep getting this error: PHP has encountered an Access Violation at 018B51CA

[shimniok]

Vacuum leak - I have resealed the tbi and adapter. The intake I have is a used Edelbrock Performer. Can these things warp? If it was an internal leak is it possible that I would be burning oil?

My new Performer manifold was warped, so, yes. Dumb question but doesn't the GM ECM tell you status of sensors as it's running?

Does a carb idle better on it?

Michael

[AlsChopShop]

have you replaced (or checked) the TPS? sounds like a TPS problem to me.

Al

[Bill USN-1]

Did you see something in his data log file that shows it bad?

[Rogue]

I've had "rolling" idle problems in the field be caused by too large an exhuast - but that is usually on Fords. I have also recently at work had two OBD1 systems with dead 02 sensors doing things I'd never encountered before. In one instance the when the computer switched to closed loop the computer would jump up from 128 BLM to 168 BLM, the engine then would stumble and remain in limbo for a minute while the computer tried to figure out what the heck was going on. No I haven't read your datalog - I'm just adding two cents based on what Mark ( DieselSJ ) said about your 02 readings. I've seen a lot of weird things in 15 years on the job and like I said - I would have never guessed an 02 sensor was causing the problems I was having with a few customers cars, yet.... they were. Good luck, Steve.

[Bill USN-1]

Maybe he dumped the FI system by now???

Been a while since he replied.

[crispyboy]

I was finally able to get back to the project.

Intake manifold - had it planed - warped about 7 thousands of an inch.
replaced throttle position sensor as a recommendation from Howell. Still idles at 3.6%. IAC is approximately 28.
Got one more chip from Howell - 6 total chips - whew...The last chip seems to be the best so far. The blm's are at 128 at idle through 1200 rpm - jump around a bit at higher rpms. Range from 99 to 146 but these where the extremes - seemed like spikes - mostly it stayed in a window of 120 through 135 throughout the rpm range.
It does not stall anymore. I can put it in gear, make quick stops etc... Rpm dips some but seems to rebound quickly.
I will now put a license, insurance and tires on the vehicle and start driving it on a regular basis. I have not ruled out a trip to Howell as I think the idle is only fair - seems to range from 675 to 750.

[82Waggy]

I wonder what your vacuum reading is at Idle.

I also wonder if the high overlap of the cam you are using is causing your TBI idle troubles - intake dilution, low vac, etc.

[crispyboy]

Vacuum at idle is 15 inches.

Cam spec:
Edelbrock 2132
Advertised: int 278, exh 288
@ .050: int 204, exh 214
@ cam: int.280, exh .295
@ valve: int .448, exh .472
intake: open 3 deg atdc, close 27 deg abdc
exhaust: open 42 deg bbdc, close 8 deg btdc
lobe seperation: 110 deg, intake centerline 105 deg

[82Waggy]

Vacuum seems high enough but overlap is 68 degrees, which may be a lot for a computer controlled motor.

Edelbrock recommends a 112LSA for use with their EFI systems.

Anyway, the high overlap could be giving your system fits - just a thought.

[Bill USN-1]

I would recommend performing an initial set up procedure for your TB.
You need to set the min idle speed and adjust the TPS. Sometimes you need to elongate the holes in the TPS to allow more adjustment.

I would also like to see a BLM log if you are using winaldl for your data.

A single BLM reading at any given time is not useful. It needs to be an average over a drive. The longer the better, but at least 30 mins.

[crispyboy]

Bill,
this is a non adjustable tps. Idle speed is built into the programming - if this is what you are asking.
The throttle body on the GW is from about a 1993 gm vehicle - found this out when I had to purchase a new tps (round connector).
The throttle body on my truck is older - but the tps is also non adjustable (rectangular connector).
PM me back with you email address and I will send you a log file tonight when I get home - I use winaldl.
thanks,
Steve

[Bill USN-1]

You can slot the screw holes enough to get the TPS reading where it needs to be once you make the min idle speed adjustment.


Idle speed is controlled by the IAC.
Minimum idle speed is set by the screw on the drivers side of the TB.

Go to the BB and look at the injection forum FAQ for the procedures.

You may find that after you back the min idle screw out some, the TPS will be much closer to 0%=.54V

scoutii76 at hotmail ;) what else would it be!!

[tndonor]

None of the above......PROPANE!!!!!!!!!!

[FSJ Guy]

You shouldn't have to adjust the TPS on a GM TBI. I have a Howell system and I've NEVER adjusted the TPS.

I suspect your cam is not TBI friendly. :(

Hopefully the latest chip will work well for you.

[Bill USN-1]

I will disagree.
Just because you haven't had to, does not mean you don't need to.

You are using a system from a 305 or 350 GM engine on a 304 or 360 motor.

The base line settings for the system need to be performed.

These include the min idle speed adjust wich is mechanically connected through the throttle shaft to the TPS.

So if you adjust one you adjust the other.

His TPS is setting at 3.6% at idle.

Idle is defined in the ECM bin(program) file as less then 2.5%.IIRC
So the the ECM is technically never going into idle.

This can affect the quality of the idle.


Also....

If the min idle is too high this means the base plate is too far open.
This will result in the IAC driving down to a count of 0 and the IAC-idle air controller---can not control the idle.

All adjustments work together and need to be set to a baseline for the engine it is on.

75% of the time you can just bolt one on and engine and it will be close enough to work.

But start changing things like headers, cams, air cleaners, adjustable fuel pressure regulators...and all bets are off.

Even using a 1 wire O2 in the header collector will prevent the system from operating in closed loop at idle.

If the fuel map is tuned for the motor it's not a problem...but what engine was the fuel map designed for?????

Hope this helps to explain the importance of doing it right.

There is nothing difficult about the TBI system but there is a lot of new terminology to learn so you can compare them to a carb.

[The PIG Smith]

I have been reading this thread of posts and an a little lost.

I would like to suggest to give time and resources, to get to a point that you most comfortable with and start from there.
Meaning, you need create a baseline with what works.

In this case, maybe going back to a carb and see if the engine is healthy and runs fine.
Wouldn't a carb setup have ran poorly with the warped intake?

It's always been my troubleshooting technique to start with a known and work to the unknown, solving one unknown at a time.
This approach maybe over simplistic for this project, but my idea is sound.

[Rogue]

Good deal Steve, I know you've been fighting this thing for a long time now!

Howell should have burned a chip that would be compatible with your cam. This is not an extreme cam in any sense of the word... well... maybe to some people... extreme to me is approaching 700 lift.. anyhow...

From 1000 miles away I'd venture a guess that Bill is right on the money, Good Luck BRO

[shimniok]

FWIW my understanding is you don't need an "extreme" cam to have too much overlap for a MAP-based EFI. I may be talking out my *** here but if so, hopefully someone will clobber me. :D If valve timing at idle is such that overlap is too high, won't vacuum will be too low and/or too erratic for the computer to read and adjust to properly?

And overlap is a function of valve timing which is affected by both LSA and duration. Does Howell have any advice on max overlap (in degrees) ? How about the cam manufacturer's advice on MAP-based EFI compatibility?

While this may be one of several issues causing your problem, I would eliminate this question first, if you haven't. I wouldn't settle for any but the most definitive answer. I don't think you can have much confidence in any other troubleshooting efforts unless/until you can definitively eliminate this as a possible cause.

EDIT: Take a HUGE grain of salt with whatever I say. I don't have EFI installed, I've never played with EFI. I am sharing stuff about cams I've run across by reading, not by doing. So... I might be entirely full of it. :D That said, I buy into the TPS issue without knowing much more than theory. It makes sense that the computer has to think your throttle is on the stop to go into an idle mode. I went back and looked at the cam specs. Is that the performer cam or something hotter? At least you know what your overlap is, so you can find out whether it is going to support MAP-based EFI.

Michael

[Bill USN-1]

AFI does not recommend anything over 214° @.050 on the intake.

As mentioned earlier, most people with cams just tune for open loop at idle once the fuel table is close.
This will help eliminate the roll in idle speed from the O2 dither.

These older ECM's only sample the data about once every 1.2 seconds.

[Bill USN-1]

OK here is the log from Steve.

It is only the sensors so for the next one Steve, check all the boxes in the data log window except the raw box. That will add flags and errors to the log.

Also when you are done with the drive, go to the BLM tab and save the table there. That is the one you need to evaluate the fuel settings.

Now from this log you can see the TPS is steady at 3.6-4.1 at idle. This is in % throttle not voltage...there are 2 ways to identify the position and some people get them confused!! Especially when looking at the bin files.

You will also see that the IAC is just about 45 counts once the engine is up to temp.
For me that is fine but most like to see it lower.

Remember that the higher the IAC the more closed the throttle plate is.
The smaller the IAC number the more open the throttle setting is.

The IAC opens and closes to allow air in to control the idle speed.

So to get the IAC lower you would have to screw the idle screw in to open the throttle. This allows more air in by the throttle shaft so the IAC will not need to open as much to adjust the air.

But as I posted earlier in the thread...you need to do the initial setup procedures as posted and NOT just adjust the screw.
By doing it in the correct order, you will also know if the IAC is actually working correctly.

Now from the BLM readings it looks like the fuel is fairly close but it does have a lean spot each time you start to accelerate. The BLM's go into the kigh 140's low 150's. Very lean. 14.7 AFR is 128.

So start with the setup procedures and then lets see where the data stands. The TPS is the adjustment that may be difficult to achieve.

Your required adjustment is opposite of what you need to make for the IAC.

[waggy401]

So I was just talking with the Howell guys. This is the procedure he gave me for adjusting the idle, since mine is hunting for the correct setting and will sometimes idle at 1500+ RPM after a long drive.

On the driver's side of the throttle body there is a cone-shaped impression near the throttle lever. Drill or grind it out big enough to get a #20 or #25 Torx (size can vary) bit into the screw that lives underneath.

Jump the A & B connectors on the ALDL plug. Turn the ignition to "on." Disconnect the IAC. Start the engine, and adjust the idle. Turn the ignition off and reconnect everything. See how that does.

Bill, the Howell systems come with a 4-wire heated O2 sensor. If this doesn't work, I guess I'll get an ALDL cable so I can post my log too.

I know I have a very small vacuum leak in the cab that I can't find - but I can hear it whistle when I let off the throttle at speed. Oddly, it wasn't there before the engine was rebuilt - then again the engine wasn't pulling as much vacuum either.

The EGR is definitely affecting my off-idle acceleration. There is no hesitation when disconnected (it a new generic one), but a little bit when connected. Before I figured out that a vacuum delay valve was installed backwards, I had to floor it just to get moving. The EGR came with a package of washers to decrease the size of the opening, which the directions said were not needed for my application, but maybe I'll try one to see how it reacts.

There I go with a long post again. . .:rolleyes:

[tyndall]

So I was just talking with the Howell guys. This is the procedure he gave me for adjusting the idle, since mine is hunting for the correct setting and will sometimes idle at 1500+ RPM after a long drive. That can happen with a high tps@idle.

I know I have a very small vacuum leak in the cab that I can't find - but I can hear it whistle when I let off the throttle at speed. Oddly, it wasn't there before the engine was rebuilt - then again the engine wasn't pulling as much vacuum either. It's possible you have a vacuum leak. It's also possible what you are hearing is the IAC whistling. Known as throttle following, it opens the IAC when you give it gas. If your counts are say, 25@idle, they could be 100@2500rpm causing the noise until they come back down. And yes, it sounds like it's coming from behind the radio.

[Bill USN-1]

The EGR is definitely affecting my off-idle acceleration. There is no hesitation when disconnected (it a new generic one), but a little bit when connected. Before I figured out that a vacuum delay valve was installed backwards, I had to floor it just to get moving. The EGR came with a package of washers to decrease the size of the opening, which the directions said were not needed for my application, but maybe I'll try one to see how it reacts.


Not sure how your EGR is set up but it should not even be opening under accelleration.

The only way I would run EGR on an injected motor is to let the ECM control it like it is supposed to.

There are specific tables in the program that determine the temp, the map(vacuum), the throttle position, and the vehicle speed for when the EGR is turned on.
Then it has tables for fuel and timing corrections.

So to hook one up mechanically like on a carb set up is not going to be optimum. It is only there to meet emission rules.

If it is turning on and the ECM does not know it, then it will take time for the ECM to adjust. but what will happen is the ECM will just think it's air and will correct the fuel back to 14.7 AFR.(stoick)
So what is the EGR even doing for you?

[crispyboy]

Bill,
The only procedure I am aware of is setting the base idle. The procedue I used for setting the base idle was:

Jump A and B terminals
Turn on the key
Unplug the IAC
Remove the A and B terminal jumper
Start the motor
Adjust the idle as needed
Turn off the moter and plug in the IACI went over to the binder bulletin website in your signature (nice website BTW) but I was unable to locate the exactly what you wanted me to look for - looked the site over for at least an hour.
Please pinpoint me in the right direction.

The Howell guys told me I need to keep the IAC around 20-40 and that the tps just needs to be a solid steady number at idle. I also needed to keep the manual idle screw backed off far enough so the computer could keep the idle at 750 as programmed.
I took the vehicle for a quick drive last night - accerator response is very nice - no hesitation even with the just ok idle. Did not stall but you know when you put it in gear and the engine hunts a bit as before.

[Bill USN-1]

Injection forum
http://www.binderbulletin.org/forums/forumdisplay.php?f=75

Injection forum FAQ's...just look down the list for the topic you need.
http://www.binderbulletin.org/forums/showthread.php?t=47254

When setting the idle I shoot for about 100 less then the programmed idle when warn. This will ensure the IAC controls the idle.

For you, if you are running a cam then you may just need to go to open loop at idle once your fuel is tuned for your motor.

You can test it by simply warming it up and then let it idle.
Then disconnect the O2 while it's idling.
If the idle smoothes right out then you know the fuel is close and open loop idle will work for you.

Did you log data and save the BLM's during your drive?

[crispyboy]

Bill USN-1,
I will check the idle one more time with what I read on the Binder website. I will also try to get some more data captures in the next couple of days.

BTW I wrote the tech support at Edelbrock and here is their response.
My question:
"Hello,
I have an edelbrock #2132 camshaft, lifters, #5832 springs, #7818 timing chain and #3731 intake manifold on my AMC 360 engine. I am installing a Howell Engine Developments GM throttle body system and the company is having a rough time of getting the engine to idle smoothly. We have tried several different chips. Is this camshaft compatible with the GM throttle body system? "

Edlebrock wrote back:

"Since this cam was designed for carbureted applications only, it was not meant for EFI systems. However, we routinely recommend this cam with our own direct port EFI systems with out a problem. TBI systems are sometimes hard to tune at an idle, since fuel dribbles off of the throttle blades like a carburetor. Thanks."

[82Waggy]

Well, I still don't know if the cam is your problem but the long overlap resulting in intake dilution at low rpm coupled with the TBI trying to "figure out" what is going on is probably not an optimum combo. Consider that GM cams used with TBI usually have an LSA of 114 or more with relatively short SAE duration (next to little if any overlap).

In reading your situation though, I wonder if your mechanical idle is still high enough to prevent the IAC from functioning when you put it in gear and the idle drops under load.

My experience with TBI is with a stock 94 Suburban. I had a wandering idle that would come and go. Had it apart many times and could not find anything wrong visually. Turns out the mounting nuts would back off with the air cleaner studs that had somewhat rough threads, resulting in a vacuum leak. Cleaned mani and TBI surface, replaced base gasket, and used red loctite on the mounting nuts and no longer had a problem.

Also note that it did not like more than 0-2 degrees base timing, which I played with to try and improve power - knock sensor would back advance way off killing power anytime there was more load than cruising on a flat road. Could not tell this was happening either - never heard or felt a change. Never tripped a check engine light or code either.

Resolved both of these issues and power came back up to like new - which of course is not saying much. Would not pass idle emmisions either until this was done.

[Rogue]

I'm still concerned about your 02 sensor switching time, if your 02 sensor is lazy as Mark - DieselSJ said then closed loop idle will fluctuate. Proper 02 sensor placement is critical, the 02 sensor does not produce voltage until it reaches 600 degrees in temperature. While scanning your data at idle the 02 sensor should cross median ( 0.5v ) at least three or four times per second. If the sensor doesn't oscillate in this manner then like Bill said you will probably need to got to open loop idle. Again this is not a wild or extreme cam, a stable idle should be very possible with proper tuning and 02 sensor placement.

[crispyboy]

The O2 sensor is approximately 3 or 4 inches below the manifold to header pipe flange. It is also a heated three wire sensor.
82waggy - the Howell system does not control the timing.

[82Waggy]

The O2 sensor is approximately 3 or 4 inches below the manifold to header pipe flange. It is also a heated three wire sensor.
82waggy - the Howell system does not control the timing.

Yes, I understood that. I was just throwing out my experience with the GM system.

Note, though, that incorrect advance will change the temperature and composition of what the O2 sensor sees.

[shimniok]

"Since this cam was designed for carbureted applications only, it was not meant for EFI systems. However, we routinely recommend this cam with our own direct port EFI systems with out a problem. TBI systems are sometimes hard to tune at an idle, since fuel dribbles off of the throttle blades like a carburetor. Thanks."

Of course... their system probably runs on a MAF sensor which I would *guess* is not as sensitive as a MAP to long overlap ???

So I guess all the million or whatever GMs running TBI just don't idle worth a darn because of this fuel dribbling problem those morons at GM never knew about...?? :confused:

Michael

[Rogue]

The O2 sensor is approximately 3 or 4 inches below the manifold to header pipe flange. It is also a heated three wire sensor.
82waggy - the Howell system does not control the timing.

That should do it. Are you capable of reading 02 readings live? Once your vehicle is in closed loop and at idle the 02 sensor should switch a few times a second past median 0.5v. In fact this is so important on newer OBD2 cars 02 switch time is data value. In any event if the 02 sensor is lazy then you can have the symptoms you describe. Good luck Steve.

[Rogue]

Of course... their system probably runs on a MAF sensor which I would *guess* is not as sensitive as a MAP to long overlap ???

So I guess all the million or whatever GMs running TBI just don't idle worth a darn because of this fuel dribbling problem those morons at GM never knew about...?? :confused:

Michael

the MAP sensor will read as steady as a vacuum gauge. if the vacuum gauge oscillates then the MAP sensor will also and vice versa.

actually since this same "dribbling problem" is a natural occurence in a carbureted vehicle ( to read a highly technical explanation as to why - pages 12 - 15 in How to Tune & Modify Carburetor Performance 1997 by Motorbooks International - basically air/fuel mixture has to flow at 35 mph to remain suspended in vaporization and when flowing through the manifold going through turns with a 3" radius exposes the mixture up to 337 G which causes the fuel droplets to fall out of suspension ) then the "carbureted" camshaft should have no problem handling this phenonmenon.

[crispyboy]

Rogue,
Winaldl allows me to watch the o2 sensor readings live and they are included in the data stream. I have compared these to the readings from my truck (stock cam). The readings for this system seem to have a greater variation. GW - 0.04 to 0.9 and the truck is 0.2 to 0.8.
The O2 sensor is new but the readings seemed the same as the old one.

[waggy401]

This is the part you need to adjust for the idle on a Howell system - others should be similar. Note where material was removed to access the adjustment screw.

http://i158.photobucket.com/albums/t96/waggy401/Wagoneer%20Rebuild/IMG_1228.jpg
http://i158.photobucket.com/albums/t96/waggy401/Wagoneer%20Rebuild/IMG_1229.jpg
http://i158.photobucket.com/albums/t96/waggy401/Wagoneer%20Rebuild/IMG_1230.jpg

[crispyboy]

thank you for the pictures - been there, done that several times.
I have another chip on the way. I took a few drives to work this week and took some data captures. It is running lean on the highway. If I can get the highway rpm's blm numbers in an acceptable range I may just take a trip to Michigan. Howell is about 330 miles from my house so one day off of work should suffice. They said it would take a few hours and would not charge me for shop time. I have all this time, effor and $$ tied up in this darn thing and I really enjoyed the throttle respone the other day I could cash in a day of work to get this fixed.

I'll keep you posted on this soap opera.

[Rogue]

Steve, that would tell me that the switch time is good which means the 02 and the computer are doing exactly what they are supposed to be doing, that is good! Now as far as the sweep range as you've already figured as being different is on the rich side. If you can read your injector pulse width at idle it usually runs about 3.5ms. i reread through the post but i didn't see - what are your hot idle IAC counts.

[crispyboy]

Ok folks - I have a TBI update. I took the day off work yesterday and went to Howell's facility in Michigan. The wagon was running good enough to make the 340 mile one way drive.
It took us about 5 hours of trouble shooting and trying different things and we found out a few things.
1.) Some tbi's have only a manifold vacuum source (on the back) for the map sensor. My tbi has two ports on the front for ported vacuum only. Check yours so you can hook your distributor up to manifold vacuum for your other than stock cams. (not sure how I did not find this before).
2.) Map sensor - my map sensor was only working intermintently. It would give the computer just enough good data to run ok but we voltage values were high revealing low manifold vacuum to zero manifold vacuum. It did not throw any codes to show up with the check engine light.
3.) Adjusted the timing several different ways. This edelbrock cam liked 15 degrees.
4.) Fuel mixture - had to tune the vehicle on the fly! This was nice. I drove and the Howell tech worked the computer. The edelbrock cam likes to run rich (blm 108 - 112 at idle) and above 1200 rpm would yield numbers closer to 127 to 129. I drove different speeds and the tech adjusted the ratio at the different rpm ranges. He also built a few steps into the idle so it would not drop so bad when coming to a stop or dropping it into gear. (beforehand the rpm would drop down to 475 and almost stall).

I'm happy I got the vehicle running though I'm not sure I would go through all the hassle again because it has been frustrating. If you have a stock cam in your vehicle hooking up this system would be easy as their stock chip is tried and true from the amount of systems they have on the market. All the employees have been working there from 10 to 12 years so they are a solid outfit. It was neat seeing the boxes upon boxes of tbi parts on the shelf. Pallets full of old tbi's and wiring harnesses everywhere. The employees were all very nice and helpful. I was really impressed that they did not charge me a nickle for coming up their and spending over half a day with their main programming/troubleshooting man. (I slipped him a few bucks because he has been helping me with this problem for quite some time.) This really surprised me because I purchased this system from a board member here about 5 years ago.
If you have a cam different from stock you will definitely need to send data captures and swap a few different chips. This will take some time so plan accordingly. From talking to these guys they can make a chip work for almost any cam unless it is so radical - you probably wouldn't want it in your fsj anyway.
The owner is Bill Howell a retired GM engineer but I did not get to meet him. Apparently Mr. Howell is also good friends with Vic Edelbrock but I doubt you will ever see a port injection like Edelbrocks come from Howell. If Howell ever sees a lucrative market for this maybe it would change. There was 4 full time guys there making wiring harnesses and taking turns answering the phones along with the secretary and the main programmer.

Thanks all for your help and support along the way in making this vehicle run. Now if I could only afford to drive it with gas at $3.19 a gallon......
My fuel milage was 12.8 on the trip up with the cruise set at 60 mph and 14.8 on the way home with the cruise set on 65 mph including two traffic jams in Detroit. Oh speaking of that rat hole called Detroit - watch out for kids throwing rocks from overpasses. I swerved just in time and they missed me.

[waggy401]

So that was you! I tried calling Troy yesterday and they said he was "out working on a customer's car." My first thought was that it was you since you had been threating to drive out there. :fsj:

Glad to hear it is running well now.

[82Waggy]

3.) Adjusted the timing several different ways. This edelbrock cam liked 15 degrees.

Many are under the misconception that camshafts alter required ignition timing, but camshafts in fact have little or nothing to do with ignition timing.

Think about it. Ignition takes place in the top half of the compression stroke. The intake valve closes in the bottom half of the compression stroke - long before the spark is set off, and the exhaust valve does not open until the bottom half of the power stroke - long after ignition has taken place.

[Rogue]

Good deal Steve! :thumbsup:

Have fun driving it :drivin: