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1996 grand am 2.4 problems


chevy05
12-29-2011, 01:00 PM
I am working on a 96 grand am 2.4 that has the wonderful P0300 code. I have unhooked the exhaust at the manifold to make sure it was not a clogged cat. That did not fix it. I also pulled the plugs and all 4 look good and looking to be firing the same. I also replaced the coil housing since I have read that is a common problem. I did notice when you rev it up right at 3800rpm it sounds like it is hitting a rev limiter and bounces back to about 3200. I also noticed while running and when the ck engine light comes on at the same time the electric fan comes on. If I shut the light of with scanner the fan turns off until the light comes back. This is the only code I am getting. I was told she was driving and was about 1/2 mile from her house and it started to act up and she barely made it home. I am using software on my laptop (pro scan). I am also not sure if there is a way to test the ICM

Tech II
12-29-2011, 04:35 PM
Does it misfire at idle or only under a load?

You replaced the tower, how were the 4 "boots"?

It's possible the PCM commands the fan on, when the misfire code sets....

Yes, the PCM prevents the engine from over revving.....

Pull vac line off the fuel pressure regulator and see if there is fuel in the vac line...

Yes the housing is the usual problem......but it could also be the ICM or coils......does your scan tool tell you if a particular cylinder is misfiring? If it shows one specific cylinder misfiring, swap the coils......if the problem moves to another cylinder it's the coil.....if it stays on the same cylinder, and compression on BOTH paired cylinders are ok, and BOTH paired plugs are ok, then probably ICM......

chevy05
12-29-2011, 05:42 PM
It misfires at idle and under a load. The 4 boots seem to be ok, they don't have buildup in either end. I did pull vac line off the fuel pressure regulator and there is no fuel in the vac line and it does have vacuum. No, my scan tool is only telling me multi engine misfire, so I have no way to tell which one is misfiring, otherwise I would switch coils around. I checked compression on all 4 cylinders I had 200 on the low and 210 on the high side. I hate to throw a $160 ICM on it, is there anyway to tell if that really is the problem?

Tech II
12-30-2011, 06:50 AM
There are two possibilities here......you could have a secondary ignition problem, OR it could be an injector problem, since compression it ok......

You would have to do a coil output test....this would involve removing the top cover and buying a set of ignition wires and connection the top cover to the spark plugs(boots would be removed).....then using a spark tester, on one wire at a time......

If spark is bad on one, then you swap coils and see if the problem moves(then it's a coil).....if the problem doesn't move, it's the ICM.....

Here is where it's a tough call....if you have good spark across the board, could be an injector or ICM....

chevy05
12-30-2011, 10:12 AM
Okay this morning I went and had the ICM tested at advance they tested it four times and always tested bad to replace it. I got one and also went ahead and got a new set of plug boots put it all back together and still same thing. I went ahead and pulled the vac line from the fpr again and had some fuel there not much very little. When I give it gas covering the rubber hose, fuel comes out of the top of the fpr. Does this mean the fpr is my problem or does this mean something else.

chevy05
12-30-2011, 01:51 PM
Well I ended going to get a FPR seeing everything I have read fuel in the vac hose or fuel coming out the top means it is bad. So I replaced it and it still misses really bad I tried to move it around and barely has enough power to drive. I am not sure what else to try still has the p0300 code.

Tech II
12-30-2011, 06:13 PM
About the only thing left is the coil(s).....also check the vac line to the MAP sensor for cracks......

chevy05
12-30-2011, 08:52 PM
Okay well I just got done working on the car thanks for all the help I ended up replacing the plugs and both coils also figuring that was the only thing left and it seems to run great know and went ahead and replaced front pads and rotors.

chevy05
12-31-2011, 10:34 PM
I also am looking to buy a new or used obd II scanner I was thinking about gensiys since it would do everything and I also need to scan abs here and there. Would it of told me that the coil was bad on this car right of the back. Or is there another scanner that will do everything it does for maybe a better deal.

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