2,500 RPMs idle when the engine gets hot?

2001 CHEVROLET VENTURE
211,000 MILES • 3.4L • 6 CYL • 2WD • AUTOMATIC
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PATTERCW
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When driving 50+ miles or more the engine will start to idle at 2,500 RPMs. The temporary fix is to turn the key off then on. The RPMs go back to 700. When driving on the highway. I can put the car into Neutral and turn the key on/off and that will temporarily fix the issue. Cleaned the TB, replaced the TPS. Same issue. What is strange is the recycling of the ignition fixes the issue right away. If I continue to drive after a while the rpms will return to 2,500 +. Driving 25 miles to a destination does not seem to activate the issue.
Oct 30, 2023 at 5:48 AM
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STRAILER
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This sounds like the PCM is bad, I would remove it and send it in for testing, but can I ask if you replaced the IAC motor? Also, let's run the codes to see if any are stored.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If no codes are stored let's, try replacing the IAC first and if that does not help the PCM. Check out the images (below). Please let us know what happens.
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Oct 30, 2023 at 12:16 PM
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PATTERCW
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Hi Ken. Thanks for the reply. I want to give a little more detail on this issue. This problem has been happening for 3-4 years. I drive about 3 miles to work each day. So, the problem only shows up on long trips. Yes, I have replaced the IAC. (About 2 years ago) also replaced the coolant temperature sensor. I see there are some companies on the internet that sell a pre-programmed PCM unit. Are they plug and play?
Oct 31, 2023 at 5:19 AM
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STRAILER
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Yes, the PCM will be pre programmed and ready to go. It sounds like it is bad.
Oct 31, 2023 at 9:49 AM
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PATTERCW
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Thanks again. Not sure if I want to spend the money. If I do I will come back and update the post.
Oct 31, 2023 at 10:09 AM
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STRAILER
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Sounds good, have a nice week.
Oct 31, 2023 at 10:12 AM