Pulsing/Surging Idle

Hello again gentlemen. My father and I have finally got the Jeep running with the 350 chevy transplant.

I have a question though.

In the last few days it has developed a problem. While parked in idle the engine will surge and fade sometimes stalling out. It can run very rough after startup. The other day while driving it the idle slowly crept up to about 2500 RPMs causing the engine to overheat. Sometimes it will run fine with no problems. We hooked it up the the computer and it was throwing a code 44 lean (O2 sensor). We replaced the O2 sensor with no change. Fuel delivery seems to be fine. TPS is new. IAC is new. Injectors are new.

Does anyone else have any suggestions as to what could be causing this?

Thanks,
Dan

any vaccum leaks along the intake?

What generation 350 are you running. If it's one of the early Lt1's with the Optispark that could also cause a surging problem.
My 94 Z28 had a similar problem and it was the Opti.
Other Posibilities vacuum leak as mentioned above or the a sticking EGR valve if so equiped.

It WAS the EGR valve. On further inspection we realized that we had not replaced it with a new one. Once replaced the loping is gone.

It seems that the idle is a little high now (100 rpms or so). Should we readjust the base timing now with the new EGR valve?

Everything else seems to be running well.

Thanks again for all of your help.

Dan