I have a 94 Gt with an Incon 800tti kit. I've been having a problem with a miss. Originally I found a bad plug wire, then my MSD6AL went out so I bought a new one and also a blaster coil. But the miss is back and now it's getting worse, especially over 1500rpms. Occasionally I can even feel it miss on the highway, like someone quickly switched the ignition off and back on.

I have also replaced all plugs (autolites gapped at .030) and have looked over the plug wires a couple of different times (no burnt spots, no spark arching).

About the only things left in the ignition that I haven't replaced are the distributor, cap and rotor. I have also considered something like a valvetrain problem.

The car doesn't seem to miss when it's cold and I first start it up, but after it runs for a short bit, it's like a switch is flipped and it starts missing, maybe it's when it changes from it's cold start map in the ECU? Even if I'm holding it at a steady rpm, when this happens, the rpms will drop and bounce. You can hear and feel it missing.

It's always had kind of a crappy idle which I have attributed to the tune, but it never missed above idle. As I said, whatever it is has gotten worse in the last couple of weeks.

This car has a bunch of miles on it (140k). I am wondering if maybe the bushings in the distributor might be worn out making the shaft wobble? I haven't checked it yet but want to this weekend, although without a correct/new distributor to compare it to, I'm not sure I can tell how much wobble is too much?

What are your thoughts? What are some things I can check? How can I rule out a problem in the valvetrain?

 

Step one, replace the cap and rotor, especially if it is stock. That costs a whole $15?

Are your wires crossed and are they crappy wires?

I put a set of 9.5mm garbage wires on my car and it had similar symptoms... because the wires had crappy insulation and arced to the block/each other.

 

I'm going to change the cap/rotor tomorrow. Yes they are stock.

No crossed wires. It's got 8.5mm MSD wires.

 

step one would be to run a koer test and check for codes to make sure closed loop operation inputs are in working order not slap parts cause they are cheap

 

+1 to pulling the codes. You may get something as simple as a sensor out of range.

Also, is the miss under a load only, or while cruising? Does it miss while you're pulling vacuum or only when under boost?

 

I will try pulling codes, but I hate this ODBI, it never provides much info, usually only a rear O2 error that it's had for years. But I will try it to see if there are any new codes, or clear them, drive it and pull them again.

It used to only miss under 5+psi of boost, but now it misses everywhere, vacuum, boost, low rpm, midrange, etc.

 

check your fuel pressure. i had a similar problem was the fuel pump. seemed like car was missing but it did it cold and hot.

 

ignition stator.

 

KOER then do cylinder balance to go to correct cylinder so can narrow down where to work.

 

i'll go with fuel pressure on this one, seeing as how i had the same problem when my car was hot. fuel pump heated up and started cutting out under load. at optimal temperatures, it was running 10 psi, as opposed to 35ish, where it should have been!