So I replaced my Opti on Saturday, since the original had 151,000 miles on it. Car ran like a raped ape all of Saturday and part of Sunday. Then it started missing only in the very upper RPM's and, now it misses/pops/backfures/runs like complete s**t under any load whatsoever. Sometimes it smooths out a little, but overall it runs rough. As I said, opti is new, as well as the coil, plugs, and fuel filter. My plug wires are a couple of years old(Taylors). They are going to be replaced soon because I can see just a little arcing going on at night(always done that).

I am thinking the ignition control module may be the culprit, because it's the only original part left in the ignition system. This is definitely a random misfire, and not cylinder-specific, so whatever the problem is it's affecting all cylinders. What's your guy's take on this? Can a bad ICM cause these problems at all RPM's and temperatures? What have you guys done to fix this problem? Any help is greatly appreciated!

 

I'de stick with the "known" first, then if need be, speculate, test and then replace. To translate, you know the plug wires arc. If you are now providing them with more power (as in new opti which has a new cap and rotor) it's a good chance they have carbon tracked even more than before and there in could lye the problem. Since you've been misfiring, it would be advisable to replace the plugs as well.

Replace them and route them carefully. Then start speculating if they don't fix the problem. It's easy to test the ICM and the coil if that is the case.

 

Thanks Speedy! I tested the ICM and it checked out. Unplugged the MAF, still ran horribly. Decided to bypass my Mallory 685, and that completely fixed the problem. Car runs smooth as a top now! That box was only a year old, but it's junk. I'll probably get another one though, because the timing retard and window switch are nice to have while spraying.

 

UPDATE!!!!!

It wasn't the box after all! I replaced the plug wires over the weekend and decided to try plugging the box in one more time before I heaved it into the garbage can. Lo and behold it worked! Apparantly my wires were good enough to handle the stock ignition system(it ran PERFECTLY with the box disconnected) but with the box it ran like complete s**t. It wasn't even drivable. Just a heads up to those who may be experiencing the same problem.