2000 Grand Am Gt Problem HELP!

The car has 152k on it and I love it. It’s been very reliable. Recently I’ve had this problem where I’m driving and the tachometer goes crazy. It goes from 2-3k to 4 to 5 k to 1 k and back really fast. When it does this I lose some power and then it will be fine for a bit then do it again. Sometimes my car drives with no problems for 10 minutes or so, then it will do it again. It’s become worse where the car stalls, but will fire up. The check engine light never comes on. My mechanic (who I trust) replaced the alternator. It drove fine for 30 mi, then did the same thing. He checked the fuel injectors, replaced an “o” ring on one, Nothing. He replaced the ignition, drove it around town for a day and it was fine. I picked the car up and it drove fine for 20 mi then did the exact same thing. The problem is the engine light never comes on so it’s had to detect what is failing. He said that when it does it, his computer says it’s the #2 cylinder that is misfiring. The car fires up fine, idles fine, drives fine, but then seemingly at random it misfires and the tach goes crazy.

I’m sure he’s checked plugs,wires, etc.

Any ideas as to what is failing and why the Check Engine light never comes on when it does this? This has happened on the freeway doing 70 to driving on the streets. There is no rhyme or reason to when it will do it.


Sounds like corroded grounds or corroded primary ignition wires. Clean all the grounds and electrical plugs related to the primary side of the ignition. In extreme cases, it may be necessary to cut the ends of the wires and crimp/solder on new terminals.

I’ll ask him about that when I take it in tomorrow. I forgot to mention that he put a new battery in as well. He might have replaced the wires too. I know that about a year ago he spliced together the positive(?) cable since it was corroded at the battery and they are a pain to replace. Maybe it could be that, but he’s a pretty smart mechanic and he said that he did the “jiggle” test of the wires to see if that had an effect on it, which it didn’t. Thanks

Problem Solved! (knock on wood). One of the first things that my mechanic did was to replace the ignition module, however the car would run fine for a bit then do the same things. After replacing a few other parts trying to solve the problem, he figured that it had to be the ignition module and he replaced it one more time with a different one. So far so good! He told me that AC Delco has had defective ignition mods before in the past, so the new one was defective as well. So, I’m out $800 due to renting cars, having other things done to my car to try and solve the problem, where if AC Delco could just make a good part it would have been solved 2 weeks ago. You better bet that I’m writing a huge complaint letter to his AC Delco rep.