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Hello- I have a 2002 buick regal 3.8L without super charge. Upon starting the cold engine, it has very high RPM about 1500, then it increases more to about 2000 RPM after 10 seconds, then it increases again to about 3000 rpm. I turn the engine off then restart and it goes to 1200 rpm. Once the car is heated, every thing seems ok. No check engine lights. No vacuum leaks. any idea? Would you just go ahead and replace tps or IAC? Any other suggestions would be helpful thanks
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Have you tried hitting the IAC with the handle of a screwdriver while the idle is high to see if it comes down? That may give you and indication if it is the IAC or not. That is not 100% conclusive, but it helps narrow down the issue. Otherwise, if you have a scan tool with live data, you should be able to see if the ECM is commanding the idle to be higher, what the desired throttle plate angle is vs. actual and how much air is coming in from the MAF data. It would also be interesting to see if the idle calms down when you go into closed loop.
This could be a number of things, data is your friend to narrow down the possibilities.
Good luck, let us know what you find…
Thanks for the tips-Never tried hitting the iac valve. I just replaced the iac valve and it solved my problem with idling. I say I took a guess and was right. Lucky this time. Replaced it because it looked terrible with carbon all built up.
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