I have a 1994 Z28. I have had opti problems before and this is different. My car runs fine when it is cold, but once it warms up it misses bad. I thought it might be plugs and wires and replaced them with no positive results. I changed the coil and ICM. I heard that sometimes when the ICM heats up the car will miss. This did nothing. Freescan shows no codes, its running lean, 12 volts, and everything else looks normal I think. I thought maybe the fuel pump was not supplying enough fuel. I drove around all of today with a fuel pressure gauge. The pressure was around 32 at idle and 43 at WOT. I thought unplugging the MAF would make the computer stay in open loop mode incase the O2 sensors were screwed up. But it still misses bad once it warms up. I NEED HELP!

Any ideas?

 

Fuel pressure at idle should be 40 and 45 at WOT I believe, so you either have a restriction, clogged fuel filter, or bad pump.

hth

andy schuck

 

i had that problem and it was my O2s when was the last time they were changed?

 

^^ check o2s

 

I will change the fuel filter this weekend.

I changed the O2 sensors a little over a year ago because of a failure. If the filter does not do anything, I will try new O2s.

I set the FPR at 42psi so the WOT pressure is what it was. If it was a fuel problem why would it run fine before it warmed up?

 

when you floor it does it hesitate bad and skip, and barely move like it should?

 

Yes! It snaps and snarls and pops at any throttle position. Anywhere from cruising to WOT.

 

o2s, they dont do anything on cold start

 

vacuum problem?

 

I have sprayed WD-40 all over the engine while it was running with no stumbles. How do I find a vacuum leak?