Emmission test blues (No More!)

[2Stock]

I got my emmission test last Wednesday and failed on the HC and CO2 by a small margin. So I did the following:

Changed oil +(1 qt of Lucas), filter
Replaced PCV valve
Did a complete TFI upgrade: Coil, Autolite plugs .45, Dist. cap, Accl spriral .8 wires
Checked air filter
Set timing @10 BTDC @ 600RPM in drive per Hayes manual
New muffler: Magnaflow
Can of octane booster in tank of regular gas

Before the work my readings were as follows:

8/13/03
"High Speed" test 2410 RPM:

HC Standard 220 Reading:285 Fail
CO Standard 1.20 Reading: 1.88 Fail
On that date low speed 970 rpm passed Reading HC 158 and CO 0.02

Today my readings were as follow:
High speed test 2369 RPM
HC Standard 220 Reading 96 Pass
CO Standard 1.20 Reading 2.00 Fail
The low speed test RPM 793 passed: HC Standard 220 Reading: 86, CO standard 1.20 Reading: 0.05

It seems to me that there is some small thing I could do to get this number down. Looks like I will have to pay another $39.50 so I want to make sure I get it right.

Also, does it make any difference which wire they hook their machine to? First, he had it on the coil wire and when I walked over there he moved it to the #7 cylinder wire.

[ August 25, 2003, 10:39 AM: Message edited by: 2Stock ]

[2ndtimearround]

Sounds like a small leak in your cab's power valve.

Check out this site for dianostic help.

http://www.recarbco.com/technical/index.html#smog

Good luck.

Lawrence

[2Stock]

Thanks for the link. I forgot to mention that the stock 2bbl carb was professionally rebuilt and catylatic converter replaced about two years ago. I checked the vent hose on carb and it is ok (not wet).

[2Stock]

Also, I am nuts about checking the vaccuum hoses, air pump valves and other connections regularly. The air filter looks fine but (in fact) I did not replace it after a mockingbird built a nest and laid eggs while I had the transfer case out of for two weeks this spring. I started it up and ran it for a few days before I noticed it was running rich. At that time, I took the eggs and nest out of the breather tube. There could be a few feathers in it that I cannot see. I will replace it (should have thought of that before). Does anybody think I can get it to pass with a tank of high test fuel or some other additive?

[Wesdog]

One gallon of denatured alcohol per 10 gallons of fuel may help. Your timing may be off at the cruise rpm test. Could also be your cruise air/fuel mixture is a little rich or lean. A vacuum leak would affect that. You may need to find a shop to test it and adjust your timing or mixture to get it to pass before doing another formal test. An adjustible vacuum advance would be helpful if it is timing related.

Wish I could be more specific but I don't remember what causes high CO. I think it can go high when rich or lean the difference being whether the HC is also high which would indicate rich. But then lean misfire can cause high HC also. Since you have a CAT that makes determining the cause of high CO a bit tricky cause it cleans up the HC emmissions. I have a bung in my exhaust before the CAT so I can install a wideband O2 sensor to monitor A/F ratio. The bottom line is to get it on a tester and make some adjustments to fix the problem.

[ August 18, 2003, 05:55 PM: Message edited by: Wesdog ]

[2Stock]

Thanks for the info. I am still fighting this battle.
The readings are all well within range except for the CO (carbon monoxide)this = air/fuel mixture problem. The standard is 1.20 and it is still reading between 1.58 and 2.22.
Since last post, I have:
replaced a rusted gulp valve on the air pump system manifold, replaced the air filter with a K&N (ouch$), taken recently rebuilt carburator off and checked the power valve (looked ok), checked the vaccuum controls (air flow) on the air cleaner body. I found that the carb. was not bolted down very good and thought BINGO! when I saw the carbon buildup at the base - but no such luck. It failed again today.

On the air cleaner air flow dampers I am mystified. I am not sure that they are working right. Also there is a blue plastic vaccuum valve on the back side that I was told was a thermostat. One of the inlet tubes is broken off and it is not making a good connection to the plug. Could this be the main problem? I have looked at everything else I could think of. I know that worn valve guides can cause a problem and I admit that there is some noise from the tappets. I just can't imagine that it is so bad that, if everything else were right, it would cause the failure.

Right now, I am waiting for it to cool of and I will take the carb off and have another look.

[2Stock]

Edit: From looking at the vaccuum schematic, the blue plastic vaccuum valve described above is labeled "Toc Temp Sen"
question: is this critical to air/fuel mixture?

[2Stock]

Nothing like answering my own questions. I found some information in the archives on carb adjustment and it may solve my problem.

http://www.ifsja.org/ubb/ultimatebb.php?ubb=get_topic;f=10;t=000048

It is the part that says that any repair of a vaccuum leak or some mods will necessitate the re-adjustment of the mixture needles. When I took the carb off and put a new gasket on it, I just put the mixture needles back to what I remember as stock settings ie. 1 1/2 to 1 3/4 turns out. I think I have to reset the mixture with my tach and by ear as it says in the link.

[Wesdog]

The air cleaner thermostatic switch is necessary for the vacuum actuated heated air diverter valves in the air cleaner snout to work correctly if the vacuum signal is connected to the air cleaner. You don't want the air cleaner routing hot air off of the exhaust manifold to the carb when the engine is at operating temp. Has the thermostatic switch just been bypassed or is there currently no vacuum signal applied to the air cleaner?

If you have fixed a vacuum leak at the base of the carb then you will have to readjust the idle mixture. You will probably need to have the idle mixture adjusted by someone with the equipment to check your emissions while doing it. Otherwise you are going to probably continue failing the test.

When you say you failed again exactly which test failed? Carb float level can affect your cruise A/F mixture as can vacuum leaks and egr valve operation. If your air cleaner is routing heated air to the carb that isn't helping either. It is helpful to know what is failing.

[ August 23, 2003, 08:02 AM: Message edited by: Wesdog ]

[2Stock]

Wesdog: Thanks for the explanation of the thermostatic switch. To the best of my memory, it was ok when I first took the test but one of the tubes got broken along the way. I have repaired it by patching another plastic tube over the end of it. Now the hose plug fits tightly and the vaccuum is continuous. I have not had a chance to check the operation of the diverter valves in the snout. Will do that shortly.

After reading the archive post referenced above, I figured that I had better check the timing again too as I have been setting it with the vac leak at the base of the carb. The idle mixture screws are just turned out 1 3/4 turns each. I don't know ANY mechanics here I trust so I will try the adjustment according to the archive post instruction. I used to have to "lean out" my '84 GW to get it to pass. Just didn't think about it with my '91. The place I am having it inspected (Texaco Oil Change)has been allowing me to do "test inspections" since the second failure. I was so sure it would pass after fixing the leak, I paid again so I guess I have some more "test inspections" coming.

Here are the readings from the last test:
At cruise 2650 rpm:

HC Standard 220 Reading 78
CO Standard 1.20 Reading 2.22

At idle 946 rpm:

HC Standard 220 Reading 65
CO Standard 1.20 Reading 0.03

[2Stock]

UPDATE: I just adjusted the carb to "lean roll" and, from where it was at 1 3/4 out, I got only about 1/4 turn (or less) in before it started lagging. I checked my timing again and it had retarded slightly (from before bolting carb down) to about 11+ degrees. So I re-adjusted it to even 10BTDC. I wonder if, as some others have said, I would get a leaner burn if I advanced the timing a little more.

I checked the front damper in the snout and it was full up, ie. only pulling air from the manifold tube. It never changed as the car warmed. I wonder if I should remove it from the vac motor and block it for now. I don't think I will need it (damper) till it gets cold. The rear damper was full open so that is ok.

I hope that gives you enough info to work with.

Also: I have seen the power valve and it looks new but how do I know if it is leaking (by physically inspecting it)?

[ August 23, 2003, 11:29 AM: Message edited by: 2Stock ]

[Wesdog]

1st- setting the initial timing: when you set the initial timing you want to insure you are not getting any mechanical or vacuum advance applied. Disconnect the vacuum line from the distributor and cap it. If carb is set up correctly there shouldn't be vacuum present at idle anyway but disconnect it to be certain. To insure there is no mecanical advance being applied lower the idle rpm to around 550-600 and then set your initial advance to your engine's spec using a timing light. Lock down the distributor and adjust your idle rpm back to where it's specified for your vehicle and then check it with the timing light. Depending on what your idle rpm is you will probably see a slight mechanical timing advance from the initial setting. This is fine. If you're getting any vacuum signal at the carb ported vacuum source at idle then there is a problem with the carb adjustment in my opinion. With the initial timing and carb properly adjusted there should not be a vacuum signal present at the carb ported vacuum nipple at idle rpm.

Timing does NOT affect your Air/Fuel ratio but it does very much affect combustion which in turn affects the content of the exhaust gases. Air/Vacuum leaks and your carb adjustments and calibrations affect your Air/Fuel ratio. So does EGR cause it injects exhaust gases into the A/F mixture at cruise and that changes the mixture slightly. Ideally the exhaust gases are inert and only take up space in the combustion chamber but in reality they aren't completely inert and contain some fuel and oxygen so they do affect the A/F ratio. Is your EGR system functioning correctly? Sometimes the exhaust opening to the EGR valve gets plugged up with carbon and prevents correct EGR operation. Since EGR affects cruise and not idle you may want to check it's opeartion.

If your CO is high at cruise it may be caused by a lean condition such as the result of the vacuum leak you recently found. It could also be caused by timing I believe. Problem is I'm not sure which way to adjust it because there are other factors that could be at work. Disable the air cleaner heated air valves for now if you can't fix or replace the thermostatic switch. You don't want heated air being used by your engine for the test. The air temp does affect A/F ratio slightly and I think there are other things it can affect as far as the test so just make sure it's not setting those flappers to the heated air position.

I know nothing about your specific carb so I can't help with the power valve question. I do know that carb fuel float level will affect A/F ratio so make certain it is properly set up. I think it can be changed to slightly to affect mixture but you'd be getting into subtle areas of tweaking that you probably don't want to go. You are so close to passing it would seem like there is just a small tweak needed to get you past the cruise CO issue. Make sure all your vacuum lines are good and not leaking. Make sure the air cleaner is supplying outside cool air through the snorkle and fresh air hose. You can use the old BB in the vacuum line trick here so it looks like it's connected and functioning correctly.
See what it indicates in another pretest inspection after your have it all working correctly. If it still won't pass you may try plugging the vacuum advance line to retard the timing at cruise and see if that helps or hurts. If it fixes the problem then you may need to get an adjustible vacuum advance and decrease it's effect or plug the line with a BB and hope the inspector doesn't notice.
If retarding the total timing makes it worse then reconnect the normal vacuum advance setup and increase the initial timing a couple degrees and see if that helps. This will affect both cruise and idle testing and if your initial timing is above spec that may cause you to fail the test also.

[ August 24, 2003, 10:19 PM: Message edited by: Wesdog ]

[2Stock]

Wesdog: Many thanks for the comprehensive explanation. Sorry I forgot to mention that it is a Autolite 2bbl carb. (2100 or 2150 I don't see an ID tag). I have the specs for the float level and will check it out. Also, I will check for a vac signal at idle with the advance installed vs. plugged. I always set the timing with the line plugged. What I see when setting the RPM at 550-600 is a little surging of about 20 rpm. Trying to adjust this out but does not respond to anything I have done. I already plugged the air inlet vac motor line. Will check the EGR valve.

I will have another pretest on Monday and see what happens. I will report back with the results.

[Wesdog]

I wasn't suggesting you adjust your carb idle mixture @ 600 rpms, only the initial timing. The low rpm for the initial advance adjustment is just to insure the mechanical advance is not affecting your initial timing setting. What I was suggesting is put the vehicle in park, adjust idle speed to 600 using the idle stop adjustment and set your timing. Then set the idle rpm to spec and adjust your idle mixture. If the spec is 600 - 700 rpms with the transmission in drive and the parking brake set then set it to that. I guess either way will work as long as the rpm is below the mechanical advance curve start. Do you adjust your idle MIXTURE with the transmission in drive and at the specified rpm or with it in park and at whatever rpm that ends up being?

What is the specified idle rpm for your vehicle?

[ August 23, 2003, 03:51 PM: Message edited by: Wesdog ]

[Wesdog]

Also check that your mechanical advance is operating freely and returning back to it's stops. If it sticks it can cause your timing to vary and make proper/consistant initial timing setup difficult.

[2Stock]

I had not looked at the specs on the car sticker before. I was using the Hays manual that said to set the timing at 600rpm in drive.

I adjusted the idle mixture in neutral with the idle at about 600 - 700 RPM after I took it out of drive and hooked up the advance hose. I haven't checked the vac on the advance coming out of the carb at idle (N) yet. I do remember visually checking it with the timing light after I hooked it back up and there was no apparent difference.

Here is what the sticker on the firewall says:

Curb Idle 600 +-50 Drive
Base Idle 500 +0 -50 Neutral

I don't know how to check the mechanical advance. Do you mean take the dist cap off and check the springs?

[Chevelleguy]

CO is partially burned fuel. You need a little more air. See if Texaco will let you run the test with the air cleaner lid removed or with a small vacuum line removed. If it won't go, the shop I work at in Mesquite does inspections, we can make it pass. E-mail me if you'r interested and I'll give you an address.

[Wesdog]

Chevelleguy, thanks for joining in here! So if carbon dioxide is partially burned fuel and more air is needed does that mean the mixture is rich at cruise? (If so why are the HC readings low, is the CAT taking care of the HC but not the CO?) Or is more timing advance needed at cruise to allow the combustion process to complete in the power stroke? Or could it be so lean at cruise that there is a lean misfire problem in which case there is too much air? Or am I thinking too much maybe and it's time for a beer.? So many questions and so little beer!

[ August 25, 2003, 08:14 PM: Message edited by: Wesdog ]

[2Stock]

DEFINITELY BEER TIME! Just watch out for the breathalizer test....many, many years ago I registered 2.0 on a blood test and that cost me as much as getting my GW fixed for this inspection. How much Tequila would I have to put in the tank to make sure I would pass?

chevelleguy: If I don't pass on Monday I will mail you.

[Wesdog]

Originally posted by 2Stock:
... I don't know how to check the mechanical advance. Do you mean take the dist cap off and check the springs?Yes, check that the weights/springs move smoothly and return the rotor to the fully retracted weight/spring position. If you find the mechanical advance corroded or binding it may need to serviced. Serviced means disassembled/cleaned/lubed/reassembled. This is probably not the source of your problems. The reason I brought it up is it appeared from your discriptions that your initial timing may be changing and this would be my 1st suspicion.

[Chevelleguy]

As close as you are, go to O'reilley or AutoZone and get some RXP(gas additive). That should do it.

[2Stock]

chevelleguy: I tried that before it failed the second time. I put in a couple of pints of alcohol too. My best guess is that, since tstat in the air cleaner was not working and it was diverting all of the air from around the exhaust manifold to the intake, that this was the main problem. I have disabled the vac to that flapper. Also, I have adjusted the mixture screw in a little.

All comments here are much appreciated. You guys have always come up with very good input.

[illegalFSJ]

I know it sounds a bit dumb, but I've had really good luck many times with just removing the air filter entirely. I usually pull off the road just before the test station and remove the air filter and throw it under some blankets on the floor, then pass the test, drive around the block and re-install the filter.
It really helps to just get a bit more air into the system to lean it out a bit.
To be honest however, I've only done this with late-model fuel injected imports (and had great sucess when nothing else would make it pass) because none of my FSJs have had to pass emissions testing.

[2Stock]

Finally Made It!

Got the CO down to .97 by disabling the front vac motor on the snout and leaning the idle screw 1/4 turn. All of the other readings remained about the same.

Wesdog, chevelleguy, IllegalFSJ: Again thanks for the good input - couldn't have done it without you.

chevelleguy, I'm sending you more mail about my F250.

[Wesdog]

Yeah!

[JeepBountyHunter]

Hey just reading this post, has given me some new insights..thanks guys!!!!