97 tranport high idle and turn signal

[ibonz]

I own a 1997 pontiac transport with approximately 185000 km. This past weekend in heavy traffic and relatively warm weather (30+ C) the van began to idle high (2500 rpm), driving almost as if the throttle was stuck (ac was running). Pulled off the highway fiddled with the throttle cable, however no change. I pulled the PCM fuse to reset the codes (Hanes manaul mentioned this worked). Fired up the van again and everything was fine, idling normal (about 750 rpm). This happened again this morning when I was again stuck in traffic with the defrost running. Again i pulled the PCM fuse and this has seemed to fix things for now. Seems to only act up when the a/c or defrost is running and the outdoor temperature is relatively warm and I am stuck in heavy traffic. I am getting my mechanic to check the codes later this week so hopefully that will give some insight to the problem. any comments would be helpful.

As well the drivers side turn signal light does not work while the signal is on or the daytime running lights are on. When the full head light package is on it works. The bulb has been replaced and is working fine. The socket is $150 or so from the dealer (no one else seems to sell them) and i don't want to replace it if i don't have to. any comments?

[Adelaat]

Am experiencing the exact same symptoms with my 1993 3.8L Transport with 285000 km. Periodically idles goes from 750 to about 2000 and when this happens, overdrive doesn't work and cruise control also won't engage. Restarting the motor will usually reset it back to normal but sometimes won't. Driving the van at 80-100 kph will also sometimes cause it to return to normal. When the idle goes up, the check engine light will also light up.

Also would be interested in finding out possible causes....
Thanks

[nicke66]

Originally Posted by Adelaat

Also would be interested in finding out possible causes....
Thanks

Flash out the codes then!

[Adelaat]

Too many codes came out to make an acurate deterination so I went to the wrecking yard and removed a coil/waferboard unit from a smashed up Lumina 3800 and installed it in my Transport. So far everything is working great. Total cost was $10 and a bit of grease on my shirt from squirming around in the wreck's engine compartment. Got lucky I guess.

[ibonz]

Problem went away over the winter. When the outside temperature is approximately less than 20 Celsius there is no high idling problem. Now that the outside temperature is warming up again the problem is resurfacing. I read the codes P0122. (Throttle position sensor circuit, low input).
As mentioned previously pulling the PCM fuse for several minutes alleviates the problem temporarilily. I am going to check the voltage on the TPS this weekend with a multimeter as suggested in the Haynes manual.
Any thoughts on why this would only occur when the temperatures are plus 20 Celsius. 1997 Pontiac transport with 240000km.

[ibonz]

Changed the throttle position sensor last june. That fixed the problem.

Resurfaced this morning, aghhh. However today its -10 C. Will check the voltage at the TPS and see if it needs to be replaced again.