I have a 93 Z28 and I put new injectors that are from a 95 Z. Obviously the car won't run right, idles rough, hesitates, and you can smell the gas coming out of the exhaust. I got a chip from PCM but nothing has changed. I have emailed them but was wondering if anyone has any ideas of what else it could be. I was thinking maybe a fuel pressure regulator problem perhaps? If anyone has an idea I'm all ears.

 

The 95 tune uses 24.9 #/HR injector constant. The 93 is nominally rated at 22 #/HR, but I don't know the actual constant used in the program. In any case, the worst case scenario would be a 13% increase in fuel flow. The long term fuel corrections, based on O2 sensor feedback, can pull up to 15% fuel out to correct the increased fuel flow, so it should be possible for the ECM to correct for the injector mismatch, if the long terms aren't already close to being maxed out on the negative side for some other reason.

How long have you driven the car with the 95 injectors?

The statement " I got a chip from PCM but nothing has changed." is confusing. Do you mean they (pcmforless?) corrected it for the injector size, but the engine problems did not change, or they didn't make a change for the injector size.?

An injector-to-manifold O-ring problem on one injector could cause the problem. An air leak on one injector will cause the ECM to add fuel on that bank of the engine, and the three cylinders without the O-ring problem will be running rich.

And yes, a leaking fuel pressure regulator will pour fuel into the intake manifold. Pull the vacuum compensation line off the regulator to see if it has fuel in the line. Might be a good idea to check the fuel pressure as well.