Ok here is the deal. I have been chasing a rough idle, poor fuel mileage, weak top end pull and a small misfire for the past couple months. So far I have replaced:

Plugs with all new NGK TR55s.
New MSD Blaster Coil
New 1LE intake elbow
Taylor OTVC 8mm wires
Hypertech 160 T-stat
New Fel-pro header gaskets
New fuel filter
New 02 sensors

Plugs seemed to help, so did the coil, so did the elbow, so did the taylors, and so did everything

Car runs 80% better than it did a month ago but there is still is a little problem. When I'm cruising at 65-75ish in 6th gear the car shakes pretty good like the motor is stumbling. Now all these things I've done so far have helped how the car runs except for that and a weaker topend 5K+ pull.

So I'm leaning towards 2 things, either the fuel pump doesn't like it when the car is under a load at less than 2000rpms, and causes the motor to stumble, or would a bad ICM cause this? I want to get a fuel pressure gauge and check it out but I haven't been able to locate one, any ideas where to pick one up at?

Any thoughts on it being the ICM?

HELP me!

 

i am having a very similar problem and am subscribing to this thread in hopes someone can answer. i have changed just about everything u mentioned, i just went back with stock parts. i still cant get it worked out.

 

Well today I got a fuel pressure guage hooked up, just turning the key on to prime the pump I get 41psi with no pressure loss after 5 minutes. Then took it out and did a few WOT runs with the guage still hooked up and I get 41psi still with no loss in the system.

I notice though when the car is moving but I'am not giving it any gas or just giving it slightly I have around 35-38ish psi. Is this normal?

So I still have the motor sumbling problem when the motor is at less than 2000rpm. Actually now I noticed it kinda stumbles in any gear as long as its at a low enough rpm, like under 1500rpm for 2nd, 3rd, and 4th gear, and around 1000-1700rpm for 5th, and anything under 2000rpm for 6th.

So, does anyone know if a bad ICM can cause this? I don't really feel like paying for another part that won't fix it

Also, I ordered a OBDI pcm from Madz28 today, we shall see if that fixes the problem when I get it. If thats not it I'm thinking maybe my opti is causing the problem? Although I don't see why it should because it runs great the rest of the time....

PCM
Opti
ICM
IAC?



Suggestions? Helpp!

 

Buy an ICM from Advance and try it out, if it doesn't work clean it up a bit and take it back.

I'm betting on the opti.

 

have you tried cleaning the thermistors on the MAF?

pick up some elec parts cleaners and give them a good cleaning.Just and Idea