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Toyota Repair/Low Idle problem

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Question
2009 Toyota corolla 1.8 5 spd.  Cleaned throttle body, changed plugs and gapped .44 cleaned all connectors that connect to plugs, cleaned MAF sensor with crc maf cleaner. Used dura lube injector cleaner, all ready fill tank done.  My car still idles at 600=650 at times and car shakes.  This is when it is fully warmed up. When cold idles high but no shakes, only when its warm, but fluctuates upto 800-900, for about 2-3 sec, then down to 600-650 rpm for about 4 seconds then back up again.  Then when I turn on the rear defogger, rpms go way down and shakes real bad, goes back to 650 rpm and repeats.  Even when I have the fan turn on high or turn on high beams, it just shakes and rpms drop at least to 600rpms.  Come to a sudden stop and does the same. I have not changed or cleaned the iac but not wanting to do, cause its a big jkob i assume.  This is really pissing me off, please help me out here, thanks Ted.

Answer
Hello, it doesn't have an IAC valvbe the idle speed i s controlled by the computer via the throttle position sensor and the throttle motor. Do you have a check engine light staying on, there have been some cases where the throttle body has to be replaced to cure this problem.

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Ted Ritter

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I have more than 28 years experience as toyota technician, I will be able to answer most questions related to the Toyota product line up to the present year models,I am located in the US but welcome questions from other regions of the world. When asking a question please provide specific information: year,model, engine,transmission information. Provide as much information as possible including a brief repair history if possible. I have been a volunteer here for more ten years an have answered over 16,000 questions helping Toyota owners with their problems and save thousands of dollars without any compensation, some of my answers are published on many other websites including google and various automotive forums. DONATIONS ARE VERY MUCH APPRECIATED, IF YOU HAVE RECIEVED HELPFUL INFORMATION PLEASE MAKE A DONATION. AS OF TODAY (JULY 22, 2014) ALL REQUESTED GRAPHICS, ILLUSTRATIONS, DIAGRAMS, PHOTOS, WILL REQUIRE THE MINUMUM DONATION UP FRONT.

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Toyota technician since 1979,expert in electrical systems,OBD systems,engine repair, driveability problems,EFI systems,ASE certified,Toyota master technician.
Certified Hybrid Vehicle technician.

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Toyota master technician, ASE certified in eight catagories, Hybrid vehicle certified. Toyota technical training: Engine Automatic transmission Manual transmission Drivetrain Electrical systems Brakes and chassis Air conditioning Engine performance and diagnostics Hybrid systems

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