8.2L Trans Am

Hey I have an odd problem #1 & #2 cylinders are running rich to the point of misfiring. All the others are a perfect light tan coloration. The idel mixture is set right and each screw is turned out an equal amout. My carburator has been freshly rebuilt and is a Baby dominator 750 which runs very well. I have been screwing with it for a while whith little progress. Thanks

Damon

It's unlikely the intake could have such a bad distribution problem. I know this sounds odd, but it could be oil fouling. Replace the plugs in those cylinders with fresh ones and put some miles on it. Yank them and look at the coloration. If it's dark on the porcelain the points directly at the intake valve, you're drawing oil into those cylinders (guide seals or intake gaskets that aren't sealing up at the front for whatever reason).

Here's how you know which part of the plug is pointing at the intake valve: After installing and properly torqueing the plugs make a line on the OUSTIDE of the plug porcelain with a Sharpie that points directly at the intake valve in that cylinder. Typically about 30-35* from straight-up towards the intake valve side.

8.2L Trans Am

I find it unlikely to be oil fouled (no blue smoke and under 3000 miles on new motor)and have changed them many times whith same result within 2 days. I am very sure the are fuel fouled because their is no oil residue on them and have never really beat on the motor. Happened since intake+carb swap. I am curently looking for a fuel leak or something. thanks

89Warbird

What kind of intake are you running? Any modifications to the intake? Were the heads or block milled down? What type of intake gaskets are you using? Do you have any way to check the A/F ratio other than reading the plugs?

paulmoore

What ype of manifold are you running, and has it been ported/port matched? You might have a problem with fuel puddling in the intake in the front, and when the intake valves open on cylinders 1 and 2 it could be sucking in liquid gasoline. What about your oil, how does it look/smell? If you can smell gas in the oil, then you have a problem somewhere. Also, if your piston rings aren't sealing properly on 1 and 2, then you could get some compression loss. This may result in a dead cylinder, and incomplete burning of the fuel mixture. If that mixture is not burning, then it could end up saturating the plugs as you stated in your first post. Just thinking out loud here....

8.2L Trans Am

My intake is weiand Team G with a dominator flange and has not been port matched, but the ports are very close to the port size on the heads. I use a fel-pro intake gasket; don't know the part# off hand but it matches the intake ports well. I've checked for fuel leaks (very unlikely) and have checked for a vacuum leak from under the manifold but have found nothing. Tomorrow I will do a compression check at work that is all I can think of. If I haven’t mentioned it already the entire ignition checked out to. Thanks

8.2L Trans Am

I forgot. The oil smells good.

paulmoore

Well, run the compression test for us and let us know what your readings are. When you intially broke in the motor, did you use/are still using regular oil? Jut curious because if you use synthetic in the very beginning, then the rings might not completely seat in the cylinders. If you are running synthetic, you should switch to a regular grade oil and keep it in until at least 3000 miles.

89Warbird

Okay, once again did you have the heads or block milled? I'm leaning toward you have a good seal on the intake gaskets on the front two cylinders and not on the others due to incorrect machining. It could be leaking from the top or bottom. This would cause the front two cylinders to pull in much more mixture than the other cylinders. I don't think fuel puddling is an issue as it would tend to affect the middle cylinders as well.

8.2L Trans Am

No machining done to anything. Luckly I found the problem. Figuring that #1 and 2 cylinders fire after one another I started to think that they could be jumping between the two and missfiring. Eventhough the cap is relitively new and looks fine and tested fine I replaced it and It runs fine. Should of figured it out sooner but oh well. I would still like to thank all of you for your help. So thanks for the help.

paulmoore

Glad to hear that you got it fixed! Isn't it just great when it ends up being somthing simple?!?!

10 SECONDS

I had the same problem but that was not the fix.