problems with TBI - Voltage updates/questions

[Hutti]

I just recently installed my Howell on a 360 with a performer cam and intake. Now that I drove it for at least 60-70 miles, its still not running well. I am on my 2nd chip and am working with the guys from Howell to figure it out. But since you guys have been through every imaginable scenarios already, I though I solicit some help. Here are my driving impressions

1. At 3800 rpm it feels like I have a governor. At about 3500 rpm, the engine is starting to make a deep thraoty like noise and looses a lot of power. At the 3800 mark, the noise gets pretty loud and there is absolutely no more go in the engine. I also sounds/feels like the engine is cutting out.
2. Idle holds very well at 730-750 range when warm and when I start the enginge when warm.
3. If I come to a full stop and put the waggy into Park..the idle shoots up to about 1500rpm and stays there.
4. Cold startup is fine however, until it goes into closed loop, its absolutely undriveable.
5. Overall I feel its lacking a bit of power but seems to suck down gas like crazy. Well, I guess the 1500 to 2500 rpm range is not all that bad.

I did check the timing (19* BTDC at warm idle without vacuum...I do live in Denver and the Haynes manual calls for 19* in altitude). Map sensor has a new vacuum hose. vacuum at idle is only about 10-11 inches.

Any and though is appreciated.

thanks,
Christian

[brielly]

What did howell's instructions call for on the timing? Wouldn't the haynes manual timing #'s be for a carburated engine that is not controlled by a computer?

[Hutti]

The HOwell system does not control spark timing either. They did not think 19* was out of range. They did ask why not 8 and so I told them I live in Denver, so they said I need the High Altitude version.

[jcz1978]

Sounds like some of the problems I experienced with the Howell setup on my YJ. It initially sounds like you need to check for vacuum leaks.

Where do you have the MAP sensor vacuum connected? Howell originally called for a port on the rear of the TBI (and later one of the front ports), but I found it better to use one of the manifold ports for better overall response.

Make sure the tach signal wiring is in good shape. Did you have any ignition problems before upgrading? If you're still running the stock cap/rotor/coil, I highly suggest the TFI upgrade.

Watch the oxygen sensor with a meter. The sensor I got with the kit was partially functional - the computer would go closed loop but the sensor always put out 0.45VDC and never responded to mixture changes. Replaced it and everything ran much better.

Make sure you set the "base" idle speed. It involves setting the torx stop screw on the throttle while the idle air control (IAC) motor is all the way closed. There should be a procedure for this in the manual that came with the kit. One thing I have noticed is that sometimes the IAC is slow to respond, especially after driving. This seemed to calm down after I replaced the MAP sensor. I've also unscrewed the IAC from the TBI and cleaned it off a few times...sometimes it gets stuck closed

If you have the PCV system connected, make sure there's no leaks back to the TBI. Also, check your charcoal canister if you still have one. Sometimes the diaphragm will dry rot - both of these conditions will cause a huge vacuum leak.

Last but not least: the GM ECU Howell supplies really doesn't like anything below about 11VDC. Check the voltage to the computer and make sure you have good connections.

I've had the Howell kit installed for a little over 2 years (just passed emissions too). Starts every time no matter what the temperature. Working out the bugs took some time. The programming turned out to be just right, just some bad parts initially.

[FSJ Guy]

I agree. Check the MAP connections. It should be connected DIRECTLY to manifold vac. NOTHING else. Removing most all the other sensors will result in a check engine light, but it will be driveable. Remove the MAP sensor and things get really weird. If mine wasn't $65 at the stealership (it's the so-called mini-MAP sensor), I'd carry an extra all the time. But, OTOH, they don't really go bad...

[Bill USN-1]

I disagree.
The MAP should be connected to the center rear port on the TB so it pulls full vacuum.
If you connect it to a single runner on the manifold itself you risk pulsing of the signal.

Just my .02

[waggy401]

I connect the MAP sensor to the port on the back of the TB, and it seems to work fine.

The throaty sound you hear is the butterflies on the TB opening up and letting you hear all the airflow action in the intake runners. When I was running a 4bbl carb with an open-element filter on my last two Jeeps they made the same sound when the secondaries opened up. My guess would be that there is some other issue causing the power loss - timing curve, weak spark, flow restriction somewhere.

I am also getting that weird idle thing, but not entirely sure at this point that the TBI is at fault. As I mentioned in another thread, I think the oil pump shaft is a little bent, making the dizzy bind a bit and throwing the computer off. Until I get that fixed, I can't adjust the IAC properly. YMMV.

[FSJ Guy]

I disagree.
The MAP should be connected to the center rear port on the TB so it pulls full vacuum.
If you connect it to a single runner on the manifold itself you risk pulsing of the signal.

Just my .02

Interesting theory behind that. I never thought about that. At the TB, you *would* have full vacuum, vs. just a one or two runners. Thanks!

[jcz1978]

Good point about the MAP connection location. The 258 has a manifold tap right there under the inlet, and that seems to work fine for me. (duh...the 360 is a little different )

I read a thread elsewhere (can't remember where) that had pics show the rear port connected to manifold vacuum, but coming off the idle air bypass passage after the IAC. Other TBI units run it right next to the plates. My TBI rear port comes out by the plates. Not sure if it makes a whole heck of a difference. Otherwise the TBIs were identical.

I picked up my mini MAP sensor for about $50 at Advance. Ordered it for a 96 Blazer with the 4.3.

[JeepStew]

cracked map sensor? if you put it in an out too much force on it it will break with a hairline fracuter. we just figured tha out on a 83 k-5 with a tbi. had alot of the same symptoms. just a suggestion

[Hutti]

just came back from my business trip and couldn't work on it...today when I was trying to play with it. I found that I have a short somewhere. man, when I lifted of the postive cable from the battery, I got a hughe arc. Not quite sure what happened while it was parked in my driveway...but I guess I have a new problem to chase down.

Anyway, while I was in there, I followed some of your suggestions and made sure there where no vacuum leaks. Just to make sure I don't get any leaks from the charcoal canister and etc, I plugged all vacuum ports besides the one for the heater motor and breaks.

I checked around the base of the TBI as much as i could and did not see anything bad. Maybe I just replace the brand new gaskets with newones to make sure I did not screw up on the initial install.

I guess I will leave the MAP vaccum line on the port rear of the TBI for now, but how can I make sure it acuatlly works like it should?

I followed Bill's link to the Binder Bulletin where he (I think it was bill ) suggested to check the mechanical advance. I have an HEI, how can I make sure that it still functioning correctly?

Bill, I was looking for a thread that explained all the voltage checks you are talking about on the Binderbulletin but couldn't find it (I must be blind) can you help me out here? Also, I ran from parts store to parts store trying to find a scanner for the TBI (OBD1). What is the cheapest option I can get to do some data logging maybe even real time analysis?

thanks,
Christian

[jcz1978]

People call it OBDI, but in reality all manufacturers used their own diagnostic routines and connectors, so there really wasn't a standard data language & connector like OBDII. You will need a GM ALDL scanner, which you can build pretty easily with a transistor, 2 resistors, some wire and a serial port connector. I built mine for less than $5. You can also order a pre-built cable for around $40. Your PC should have a 9-pin serial port on it, or you can pick up a USB->9-pin serial adapter pretty cheap online.

Once you have a cable, you can use a free program called WinALDL to get the data from the computer. It can show codes and real-time sensor data like o2, baro (MAP), RPM and vehicle speed if you have a VSS.

The WinALDL site has info on building a cable and the software:

http://winaldl.joby.se/

Pre-built cables:

http://www.aldlcable.com/

USB-to-Serial cable that works in this application:

http://www.newegg.com/Product/Product.aspx?Item=N82E16812147302

(Ignore the reviews, works fine on WinXP)

[Hutti]

Jim -

thanks for the good info. Do you know if WinALDL works with that USB cable they have on there?

http://www.aldlcable.com/sc/details.asp?item=aldlobd1u

thanks,
Christian

[budojeepr]

Bill, I was looking for a thread that explained all the voltage checks you are talking about on the Binderbulletin but couldn't find it (I must be blind) can you help me out here?

You ain't blind. Digging through all that can make you crazy. I knew I'd seen it, too, so I went searchin' through all my bookmarks.

This post says:

"Pull out your meter and sheet 1 of the wiring diagrams....
Look at the 2 outside columns, They are labeled.
"KEY ON" and "ENG RUNNING"
You need to do the key on voltage checks at the plugs on the back of the ECM or where they go to.
This will save a lot of time trouble shooting if the system has problems."

[waggy401]

Jim -

thanks for the good info. Do you know if WinALDL works with that USB cable they have on there?

http://www.aldlcable.com/sc/details.asp?item=aldlobd1u

thanks,
Christian

It better. I just ordered one.