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Pontiac Repair/idles too high

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QUESTION: I have a 1991 Oldsmobile Cutlass Supreme. 3.1L V6. 117,000 miles. It started to idle really high and check engine light comes on. Code 35. I changed idle air control valve and it ran perfect for a few days and started doing the same thing. I put in another idle air control valve. Same thing. Same code pops up. I can take the negative cable off the battery and it resets and will run fine for a few days and goes right back to the high idle and code 35. Any ideas? Thanks.

ANSWER: Hi Shannon:
there can  be a l;ot off reasons for this code. That engine has a very specific way to learn that valve to the engine computer if not it will set that code the original valve may have been bad and they ones you put in were not learned and are causing the issue due to not being learned. youcould have a vacuum leak for a split vacuum hose and that can cause the issue as well. with the engine running get a can of carb cleaner and spray around any cvacuum hose or fitting and see if the engine speed increases if so you found a leak. back to the learn process. first off before you do that clean the throttle body and throttle plate with that carb cleaner. then disconnect the battery and let it sit for 10 minutes reconnect the battery start the car with the a/c off. apply the parking brake. put the car in gear and let it run with the parking brake applied sit in the car so it doesn't take off on you if the brake decides to not hold the car. let it run for 10 minutes if the cooling fan comes on shut the car off. turn the car off for 1 minute start the car up again and let it run for another minute in gear. turn the car off and the Idle control valve will be learned to the engine computer if the code sets again there can be other issue but try this first. good luck :-)


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QUESTION: I did everything you said. This time it started to idle high the next day as soon as I started it. It usually goes a few days before that starts. What next? Thanks.

Answer
sounds like it's an issue with the engine control computer it's loosing it memory. or one of the input sensors is skewing the data to the engine computer and making it idle high with out the aid of a true scan tool it's just a guessing game as to it being a bad computer/

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Todd Puccio

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General auto repair,electrical issues,driveability issues,anti-lock brakes,SIR systems,HVAC,engine performance,Gm specific. I have worked at my current dealership since the 1990 model year anything much older than that I have limited exposure to. I do not have very much transmission experience so those question you may want to ask of another expert. When you send me a question let me know the exact make/model/engine and year for the car or suv you have it makes it easier to answer the questions that way. If your happy with the answer I gave you please feel free to Donate. This is a free service to you and I am not compensated at all by this web site. I have 22 years of experience to share with you and my knowledge wasn't free to me. I had to pay for my education.

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Experience in the area: I have been a technician in GM dealerships for over 22 years and I am a ASE master technician. I work at a Buick and GMC truck store Previously I worked at a Pontiac GMC store for 18 years. I Served a a lead technician when dealership was on a team system. I just recently moved to a Buick,Hummer,Saab Store when my franchise was purchased by this dealership. Organizations: ASE master technician

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ASE

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Education/Credentials:High school diploma,2 year vocational school degree 2 year college degree. Associates degree in applied sciences (auto technology)Awards and Honors: GMC master technician

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Master GMC truck technician Master ASE technician in 9 categories

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