1998 pontiac grand am se 2.4l engine is skipping and shaking?


Asked by Nov 20, 2012 at 06:33 PM about the 1998 Pontiac Grand Am 4 Dr SE Sedan

Question type: General

My car is shaking and jumping and i can not figure out what is wrong with it. It is throwing out a P0300, which is a multiple misfire. I have changed the following parts. Sensors: camshaft, crankshaft, coolant temperature, throttle position, and the fuel preasure regulator. I have also changed the timing chain, the spark plugs, fuel filter and both of the coilpacks, and it has not helped one bit. When it idles, it will not rev above 4 rpms. It will stall some times when I put it into drive. When it doesn't stall it shifts fine, but it will still not rev above 4 rpms. I am all out of Ideas. I am going to change the PCM, but i want to make sure I cove every possible avenue, before I do it. If anyone has any suggestions they would be much appreciated.

7 Answers


also the EFS off light will come on with the check engine light, and the only way you can get it to turn off is to reset the error code. It will stay off for a few minutes, then come back on with the check engine light.

1 out of 1 people think this is helpful.

Check in at GAOwnersClub.com - the members there can help you sort through the misfire.

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If it isn't going past 4000 rpms that's 1 of three things. Either its the neutral safety switch is somehow stuck reading park. When you shift the computer sees that and makes adjustments for the added load. That way you save a ton of gas while letting the car warm up on a cold day.if those adjustments aren't made then it will be under powered and run like crap. The reason it isnt passing 4000 rpm is the rev limiter. Its possible but unlikely. The next possibility is much more likely and its the exhaust is colgged, whether the cat is plugged or a pipe is bent. The third and just as likely as the second and it's the fuel pump isn't putting out enough volume to keep up with the higher rpms and your engine is getting what's called fuel cut. The engine spits, sputters, and misfires, it loses rpms and the pump catches back up because of the lowered rpms. The first possibility was thrown in there only due to the fact that 4000 rpms is the rev limit while not in gear. The second and third are very common occurrences and are just as highly likely as each other.

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your catalytic convertor is likely plugged -removed #1 h02s sensor and install a back pressure gauge -start engine and idle check gauge should be roughly 3-4 psi at idle - crack the throttle abit or have some one tap the gas pedal and watch the gauge psi will go high if cat is plugged I believe even 6 psi is to high I would replace the Cat


3 month old question


More then likely the cam is timed a tooth or two off. I had the same problem with my car

1 out of 1 people think this is helpful.

iac or coil planium top or a bad cat or a timing chain has went bad cousing it to stall out shack and rattle at stops but runs perfect while driving it finding out the cat will plug up and glow hot red at the back side of the cat but the back pressure from that being plugged up will cause back pressure to the engine causing the engine to spin backwards that then it streched the timing chain and causing the timing chain to skip a tooth or 2 ahead of time throwing the timing off on your engine i just went through all this this past week i kicked the cat out the exhaust system what that means is i cut the stupid cat out put a straight pipe in place of it cost me about 50.00 dollars with the clamps and hot heat weld putty and new timing chain set with guides and as good as new again those cats can cause a bad fire can blow up your car i changed it to a straight pipe and clamps and heat weld putty around the joints and good as new and o2 sensors work with this god bless my master degree in mechanics pays off . they do this on race cars too and on certain other vehicles as well . cats are no good but if you want to put a replacement one in go ahead you can get a replacement cat for 100.00 dollars ok have a nice day.

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