The car runs excellent till it warms up. Then it develops the infamous stumble around 2300 RPM. If I down shift it and floor it, it cleans out. What would be some items to check for before scanning the PCM(tuned by Bryan)? I need to get this thing figured out especially since now its warming up. Also usually I get the SES light when it starts to do this but the PCM doesn't seem to store the code. The T/A has a new crane cam, mildly worked LT1 heads, edelbrock headers(no cat), new opti, CSI water pump, MSD wires and coil. Any suggestions would be great.

 

I would check or replace O2's, especially if they have over 50,000 miles on them and/or exhaust leaks before the O2's.

 

Did you Verify that it's a Closed Loop Issue or does it just seem to happen warm? It could be your intake bellow is torn, your O2's are Bad, Mass-Air, Etc.

Just some places to start

 

is closed loop like running with no o2's plugged in!

 

Closed loop is when the PCM Uses inputs from all Sensors Open Loop is used during warm-Up cycle and O2 Inputs are ignored till O2's reach temprature so if it runs bad when warmed up check your O2's

 

compare your injector pulse width between the banks as you increase rpm. generally you'll catch one thats slower than the other. A lazy injector is common and sounds like your problem.

 

what year is your car? sounds like you need some tuning.

 

SORRY.... I meant to say it could be a lazy 02 sensor if the IPWs arent the same

 

The vehicle has new 02 sensors and a new 1LE bellows. Everything has been replaced on it and the PCM was tuned by PCM4LESS. The reason I believe its a closed loop problem is because it happens between 1300-2300 RPM and acts like its trying to load up but as soon as I downshift it clears out. At WOT it runs great or when its still cold and hasn't reached operating temp. Im going to contact Bryan and see if it could be a problem with the program and also I plan on pulling the plugs on the o2 sensors and running it at operating temp to see if the problem goes away.

 

hooking up a scanner can help you determine what the problem is.