So if it gets cold outside at night in the mornning when i start the car runs rough for about a minute.
This only happens if it gets like under 40 Deg out side.

 

Might be a problem with the coolant temp sensor in the water pump housing. If it isn't telling the PCM the temp is below 40*F, the PCM will not richen the mixture enough for a cold start.

 

what will unpluging it do?

What else does that sensor control?
Could it have anything to do with a high rpm stumble?

 

If you unplug it, it will tell the PCM the coolant temp is 40* below 0. The PCM will know the sensor is missing and set a code. How the engine would run at that point is anybody's guess. The coolant temp controls cold start A/F ratio, low temperature engine idle, tells the PCM when to go into closed loop, and affects the power enrichment mode target A/F ratio.

 

I have the opposite problem, when it gets cold mine wants to run pig rich on the 1st start.

 

Injuneer

power enrichment mode target A/F ratio, if that is f'ed up would/could it cause a high rpm miss-kinda like hitting a limiter?

Can you tell me what the difrence will be in PEM with it unpluged? Like less or more fuel?

 

This one never got an answer, ttt

 

Its hard enough to figure out how the engine will run when all the sensors are plugged in. You're asking me to decipher the GM hard-coded logic for defaults on loss of inputs, and I honestly have no way to do that.

 

Yea mine does the same thing. Having no cats makes it 10 times worse as well.

 

you are now only 99% as smart as i thought you where