Mine was a bad throttle body position sensor. However they are also known for bad MAP sensors.
Try unplugging the TBS and rev the motor. If you find it jumps up and down in speed, with it unplugged and plugged in then it probably is bad.
Coil packs also are a problem with the 3800. Swap them around, and/or replace all 3 before you give up.
Also I took off my Throttle Body, and took it all apart and cleaned it. It was black from the intake problem and misfiring. The idle air control plunger also was stuck and black as well. Carb spray helped there. Also did you decarbonize the intake when you had it off? And they are known for warping, so you want to replace all the orange gaskets. Another thing, be sure you replace the PCV valve which on my 95 was on left side of the intake manifold, underneath what looks like a plastic cap, resembling an oil cap.
Of the 3 motors GM made for these vans, I truly think the 3100 was the best overall, as it used a regular Aluminum intake instead of the junk PLASTIC ones used on the other 2 engines.
Sunday, September 16th, 2007 AT 11:14 PM