I have a backfire issue and I need help! [Archive] - GrandAmGT.com Forum

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orangej
04-06-2005, 11:08 PM
I have a 1992 Grand Am GT with a rebuilt engine (3.3L) in it and recently it began backfiring when I accelerate or when I am going up a slight incline or hill. I thought it was the spark plug wires so I changed them and it's still doing it. Could it be the spark plugs themselves or something else? I really need help and would appreciate anyone that can help. It's to the point now where it runs but I don't dare drive anywhere for fear of ending up stranded besides it is running too rough (injectors maybe). Another thing, when my friend changed the oil for me (cause he was borrowing it and thought he'd do it in exchange-big mistake) he overfilled it by about 3/4 of a qt. of oil. Someone suggested that the catalytic converter might be clogged (since my "friend" didn't mention the overfill til I happened to check it-was around the time it started messing up). Could it be clogged? It has "dual" exhaust and there is exhaust coming out the left tailpipes but not the right though they are connected. Also there is a hole in the right muffler. Any ideas..please I'm lost on what could be going on!!

93 GT
04-07-2005, 02:41 AM
It could very well be the cat. To test it just unbolt the exhaust system from the rear header on the engine . You may need to remove the brace by the sway bar to get to the two bolts that hold the exhaust system on. After you unbolt the exhaust system use a some wire or a bungy strap to hold it up off the ground. Put the brace back on and go for a quick spin. If the cat isn`t the problem then start looking for bad grounds and unhooked sensors.

BTW the "dual exhaust" on these cars is a joke . Its just for looks realy because its single all the way back to the first muffler then it comes out of it in the back then go`s to the other side into the other muffler. As for the hole I wouldn`t worry about it , it isn`t gonna hurt nothing .

SilverGAGT04
04-07-2005, 08:10 PM
Yep, the cat.

orangej
04-07-2005, 09:27 PM
Thanks! I had a feeling that is the problem. Also today the car died and a code 42 came up which is the wiring harness that connects to the coil pack module (pad). I took the coil pack apart and cleaned those coil terminals and that helped (before it died). I also tested those and they are fine (coil packs and the pad it sits on).
Also I've heard that drilling a hole in the front of the cat where the pipe meets would help eliminate the backfire. I tried that and maybe I did it incorrectly because the problem is still there. I'll try what you both suggested and hope I can get it running once again...Thanks

93 GT
04-07-2005, 10:30 PM
You would need to drill a purdy big hole for that to work I`d think. Then you need to weld it up or have some one weld it for you once you get it fixed .

SilverGAGT04
04-08-2005, 07:48 PM
Dont Do That!

93 GT
04-08-2005, 08:29 PM
Dont Do That!

Drilling a hole in the exhaust isn`t that big of deal at all. Its very simple to make up a patch panel and weld it on. Just be sure to unhook the battery before you go a weldin unless you think you wanna replace you`r car`s computer. As easy as all that is it will be much more simple to unbolt the exhaust at the rear exhaust manifold/header and also cheaper .

orangej
04-11-2005, 06:28 PM
Ok, I'm gonna try and replace the cat and the wiring harness that connects to that coil pad. Any advice? Hopefully that will work...if not, pushing it off a cliff may be the last resort. Should I ever buy a GA again? This one has been one headache after another and I take really good care of that car.

SilverGAGT04
04-11-2005, 06:55 PM
How many miles does this car of yours have?

orangej
04-11-2005, 07:02 PM
130,000 miles

orangej
05-04-2005, 10:43 AM
Ok, my Dad has a 93 transport and it's doing the same thing as mine. He has the 3.1 L. Does anyone know what the problem could be? I can't even get it to start (either car) to hook up a scan tool. My guess is the problem is located in the ignition somewhere...we've tested everything at Autozone and keep coming up more confused. The only difference is that my car backfires when it does run and his does not. But I think I figured out that part of it. Now we just can't get 'em to start. They sure try to start, tho...Please help if you can...Thanks!!

93 GT
05-04-2005, 12:34 PM
Did you check and or replace the wiring harness yet ? Have you checked to make sure all the injectors are working right ?

orangej
05-05-2005, 01:56 PM
Yep, I replaced the wiring harness and for some reason that didn't fix it. The code 42 still came up. We just tried to splice the part that connects to the coil pad to the wires coming off that part of the wiring harness. We didn't replace the whole thing because that would require alot of work!! I have a feeling those injectors may be bad. How do I check to see if they are bad, and if they are, how would I fix the problem? Thanks! Oh, another thing I don't think I mentioned, I had added a bottle of Lucasoil injector cleaner and gas and a few minutes after it died. I use that stuff all the time and think it's great but just wondered if there was any relation between adding it and car dying.