So Ive been having trouble with my 02 4.3l at idle. It was idling at 500 and dying when you put it in gear if you didnt allow it to warm up. Pulled the IAc sensor and it was gummed up with crap even though the throttle body was clean and found that the crankcase breather hose was falling off and creating a large vacuum leak. I replaced it and now since its about 20-30 degrees out it will idle at about 1000-1200 on cold start with the new sensor. Strangely if i turn my heat on the idle spikes everytime the compressor kicks on. Once it warms up for about 3-5 mins it drives fine although the idle is still around 500-600. My biggest concern is on cold start if i dont have time to let it warm up and put it in drive this thing will go up to about 25mph without and throttle. But like I said after 3-5 mins it drives normally. Im concerned that maybe the sensor is bad or maybe the pcm is remapping itself for the new sensor(been in for about 60 miles now). Ive heard the ECT can cause strange issues and suspect either the ECT or TPS is starting to fail because once it reaches op temp its fine. Anyone else have a similar problem? Im showing an P0155( heated 02 sensor but i replaced that 6 months ago) and a P0440( dont have a gas cap) but no other codes in the history.

 

Missing fuel cap
Defective or damaged fuel cap
Distorted or damaged Fuel Tank Filler Neck
Torn or punctured Evaporative system hose(s)
Defective Fuel Tank Sending Unit gasket or seal
Split or damaged Carbon Canister
Defective Evaporative Vent Valve and/or Evaporative Purge Valve
Defective or damaged fuel tank

 

Figured it out. Seems that the upper intake manifold gasket is leaking. Replaced the lowers during the summer but it looks like the upper is causing a vacuum leak. The truck starts when it's cold but starts acting up around op temp when everything is warm and expands. Replacing it later this week.. At least the 9 degree weather will keep me in good spirits

 

Curious, what is the idle supposed to be? My 2k1 idles at 500rpm....

 

Alot of people say 600-850. Anything below 500 usually causes a stall.

 

I don't have the problems you talked about but my 2k1 has a strange idle the rpms are normal yet it will buzz the whole car once park is engaged I cleaned the iac and throttle body, put new spark plugs and wires, did synthetic oil change, exhaust seems good, gas cap is fine, no vacuum leaks engine light isn't on, and car has 127k on it I've tried cleaning the fuel system also one thing I can say is before I bought it was sitting for about 7 months not being driven.

 

Check the motor mounts maybe? Pop the hood and have someone drop the car from park to drive or reverse and watch to see if the motor moves drastically. Only thing I could really think that would cause that much vibration. Check the heat shield for the exhaust too they rattle