PontiacBonnevilleClub.com

#4 can literally cause #2 and #3. PCMs can also be an occaisional pain point on these era cars. Same with ground busses.

I am not sure about the rest of your circumstances, but you are also in danger of the car degrading more quickly because of not being used.

Where are you located?

As long as the subframe, brake likes and fuel lines aren't about to rot out, I would fix it.

Get a cheap power steering cooler. ($30-40) You can bypass it but it'll cut some life out of the system.
Run new wire(s) to the coolant temp sensor from the plug at the firewall
Clean the TB with MAF sensor safe cleaner or remove the MAF if the coolant temp sensor re-wire doesn't work.
Get a new battery ($100ish) or go to the the junkyard. They sell used ones dirt cheap.

RJolly87 wrote:#4 can literally cause #2 and #3. PCMs can also be an occaisional pain point on these era cars. Same with ground busses.

I am not sure about the rest of your circumstances, but you are also in danger of the car degrading more quickly because of not being used.

Where are you located?

Thank you for your reply RJolly87.

I installed a new battery, and the intermittent high idle occurred again. (The intermittent high engine temperature has not re-occurred, but I've only driven the car about 20 miles.) I have the capability of monitoring the PCM inputs/outputs with a cable, laptop, and software. Can you please help me with specifically what I should monitor for both issues? And what are proper operating ranges?

Can you please also elaborate on how to check the ground busses?

That's great advice to use the vehicle more frequently. I will remember that.

Lastly, I'm located near Dayton, Ohio.

Thanks again for your help and expertise. I really appreciate it.

95naSTA wrote:As long as the subframe, brake likes and fuel lines aren't about to rot out, I would fix it.

Get a cheap power steering cooler. ($30-40) You can bypass it but it'll cut some life out of the system.
Run new wire(s) to the coolant temp sensor from the plug at the firewall
Clean the TB with MAF sensor safe cleaner or remove the MAF if the coolant temp sensor re-wire doesn't work.
Get a new battery ($100ish) or go to the the junkyard. They sell used ones dirt cheap.

Thanks for your reply 95naSTA.

Yesterday (Sat, July 6), I had a mechanic perform a thorough visual inspection of the vehicle. He said the subframe and fuel lines are fine. The one rear brake that has not been replaced "may fail in the future due to corrosion." Other than the issues in my original post, he also noted that the steering rack and pinion is slightly seeping power steering fluid and the transmission pan gasket is slightly leaking fluid; neither of these fluid issues require immediate attention. Am I correct in assuming you would still recommend fixing the vehicle?

I installed a new battery, and can install a cheap cooler and a new wire for the temp sensor. Thanks for the great advice.

Sorry, but it's not clear to me what to do for the intermittent high idle issue. As I posted in my reply above to RJolly87, "I have the capability of monitoring the PCM inputs/outputs with a cable, laptop, and software. Can you please help me with specifically what I should monitor for both intermittent issues? And what are proper operating ranges?" Or is there something simple I can try first?

Thanks again for your help and expertise. I really appreciate it.

The high idle can be caused by a back throttle position sensor or Idle air control.

I had a high idle problem on my '94 Bonneville. I cleaned the throttle body, idle air control and MAF sensor with MAF sensor cleaner fluid and changed out the upstream O2 sensor. Problem has been resolved.