I'm putting this post in the off topic area, because it has to deal with my friend's 1995 Pontiac Grand AM SE (2.3L QUAD 4 engine). I hate this car, because it is a pain to diagnose problems. Hopefully some of you have had some experience with gm cars.

Here is the story.....

The car hasn't been driven in about a year. The car initially suffered from a lack of power (took forever to get to 25 mph) and ran like crap. We did a complete tuneup (wires, coil packs, spark plugs, air filter, fuel filter). The car still ran bad. The cat was in bad shape, so it was replaced at Midas last year. The one time he drove it after the cat was replaced (her other car had some problem that day), someone told him that the exhaust was glowing red. He hasn't driven it since. A compression check showed that all four cylinders are around 180 psi.

We flipped the coil pack cover and hooked up old ignition wires to test for spark with a timing light, because there is no other way to test for spark on this car. Number 1 and 4 weren't getting spark. Switched coil packs then 2 and 3 didn't get spark. So the new coil pack that we bought was bad. Bought another coil pack and now all four cylinders were getting a spark. We put everything back together and had some trouble getting the car to start. When my friend almost had the engine ready to start (it sounded like it was ready to fire up), I heard a very loud pop and saw the top of the air filter box pop up. There was enough pressure from the throttle body that it basically broke the plastic around the screws of the top of air filter box and cracked the entire bottom edge of the filter box.

After being in shock at what I saw, we tried to figure out what the problem was. We are thinking clogged exhaust. We took of the exhaust pipe from the exhaust manifold to the cat. I saw absolutely no catalyst. I could drop a large socket into the pipe and it would immediately fall through. The longer pipe that goes over the crossmember is welded to each piece to the muffler (got to love Midas work) can not be removed unless I cut the pipe. I put a shop vac on the one end, and it was pulling quite a bit of air through there (the vac didn't have the high-pitched sound like when I put my hand over the end).

After another disappointing and frustrating day with the piece of crap pontiac QUAD 4 POS, I have one question. What could possibly cause enough pressure to make an air filter to basically explode? I am not as familiar with the QUAD 4 and welcome all suggestions.

Thanks for reading such a long post.

 

Backfiring from incorrect firing order? Is it possible to interchange the wiring harnesses to the different coil packs?

 

given the lack of power and the sudden appearance of a backfire I'd make sure the timing is still on, if it was retarded severly you'd have a big problem with power plus once all 4 cylinders were firing you've got the opportunity to create the pressure. Double check your firing order then check the timing gears.

 

It is impossible to change the firing order on that engine. It doesn't have spark plug wires. It has a plastic coil pack housing that connects to each spark plug.

 

I just wasn't sure if the coil packs had long enough wires to get them mixed up.... I seriously think you have a timing issue....

 

I found a pic of the ignition setup. basically that whole unit bolts to the intake. The coils are under that tan plastic housing. Its a nice compact setup, but it is a pain to try to figure out how to test for basic things like spark, timing, etc.

[IMG]local://upfiles/5767/75632DD4AE524092A9357D7DAED3C40A.jpg[/IMG]

 

I'd pull the timing covers and manually check it...

 

I think these are classified as GM's King throw away engines.

 

Piece of Pontiac!

Poor Old Nincompoop Though It Was A Caddilac


Ya know ...... every single Pontiac owner that I know has had nothing but problems with them ..... best bet is to drop an ecotec in if it'll fit

 

We finally figured out the problem with this car. It was a bad fuel pump (plus an "new" coil that was bad out of the box).

The reason that it was so hard to determine was that we could hear the pump turn on, but the GM engineers decided to remove the schrader valve on the fuel rail starting in 1993. Now you have to tee into the fuel line to get any sort of pressure reading. When we had the backfire and the car wasn't starting, I listened for the fuel pump and couldn't hear it. I even jumped 12V to the relay and heard nothing. The new fuel pump solved the problem.