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Toyota Repair/1991 corolla 4x4

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Expert: Ted Ritter - 6/27/2009


Question
Hi Ted,
I have a 1991 corolla wagon (4x4) that has developed a severe idle problem.   When the engine is running the idle revs up and then reverts back to normal. This happens continuously but is worse when the engine is hot. When I remove the wires to the vaccum sensor the idle remains high and when I disconnect the tube coming from the vaccum sensor the idle drops really low and the engine runs really rough but is still driveable.  I took it into ultratune but I don't think they had a clue.  They turned the idle down as far as it would go, gave a few things a clean up but didn't fix anything (a big waste of money).  They suggested the thermostat was stuck open and there was a problem with my cooling system system leading to a problem with the auto-choke.  I change the thermostat and gave the cooling system a top notch flush all to no avail.  Anyway, if you could shed some light or offer a few possiblilities that would be awesome.  Thanks Billy

Answer
Does the check engine light ever come on? Is it on at this time? If the check engine light does not turn on while driving check for a vacuum or air intake leak, check the large intake hoses from the air filter, they have a tendency to crack, check all other vacuum hoses, especially the alrger ones for any that may be cracked or have become disconnected.

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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 almost ten years an have answered over 16,000 questions helping Toyota owners with their problems without any compensation, some of my answers are published on many other websites via google and other search engines. AllExperts recently added a new feature which allows questioners to donate to experts on the site, any amount of donation is very much appreciated, to make a donation just click on the DONATE button.

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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.

Education/Credentials
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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