While driving my 94 Z in normal traffic is develops a stumbling/miss from 1700-2100 Rpm only, otherwise the car runs great. As long as the car is driving above or below this RPM range it is smooth. I have already installed an MSD opti, wires, plugs, coil, ignition module, and MAP sensor. I have OHM tested all injectors, TPS etc, with no problems. I have checked fuel pressure with and without vacuum attached and i have found the pump is about 4 pounds low on pressure, so i realize I probably need a new pump (but not critical) I have also replaced the fuel filter twice. As well as removed the intake manifold and replaced gaskets and cleaned throttle body. With all this being said and at my whits end as to what the probelm might be, on a whim the other day I removed the vacuum line from the EGR valve and plugged it and went for a drive. The car ran perfect with NO SES light coming on. My question is........could the EGR valve really be causing all this RPM specific under load driveability problem.

Thanks
Devon

 

Yes it could. My 94 started doing the same thing and it got cleared up as soon as i replaced the EGR valve on the back of the motor. It's not that difficult just kinda frustrating since you have to reach under the cowl area and all the way to the back of the engine. Give it a shot and tell us if it works.

Garry

 

I had a similar problem and just checked the engine code, which gave a list of things it could be which it sounds like you already looked at most. I know you don't have the light in, but the EGR valve was listed along with bad catalytic converter, fuel injectors, or O2 sensor