Quote Originally Posted by Junker2 View Post
I know this reply is a little slow and the thread old but the reason I asked is because I have a 93 GM 4.3 CMFI transplanted in a CJ7 that is running rich that I can't figure out why...
I have looked at everything I can think of but my INT and BLM are settled at around 108, the H2OS is >850mV and the exhaust is obviously rich. After a drive DTC 45 is set.
I have:
Reinstalled the original PCM and get the same condition.
Checked H2OS by grounding to get less than .350mV
Double checked fuel pressure
Replaced CMFI spider injection assembly and again checked for leaking
double checked fuel pressure regulator and for a clear fuel return line
Disconnected MAP for PCM value read
Checked the HO2S heater wire and system is working
No Fuel canister purge installed
TP sensor output correct and solid
ECT correct and verified

I tend to believe something is adding EMI as references pulses but I can’t see anything obvious like broken wires or incorrect grounds in the ignition system I could have missed something. How sensitive is the system?

What does the data log report for the Injector pulse width? What does the PCM send or can it read actual injector pulse? Is there a way to test that?

I am open to any other ideas at all and any help would be appreciated!

Thanks!
OK granted this post is over six months old. Have you checked that the injectors are the original type/model? Whatever injectors that are in your engine may not correspond to what the ECU thinks and/or programmed for.