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Q: Low idle problem

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I just replaced my IAC control valve and the Alternator as well because of low idle issues. Unfortunately, Iam still having the same low idle issue especially at start up in the morning. But after the car runs a while it smoothes out and drives normal until I go to start it up again and then it Idles low for a few minutes then it runs smooth . What else could be causing this problem with low idle? Also when driving on the highway at about 60 miles an hour it feels like the car jerks back as if it's not in overdrive. Please help me figure out what's caising me this problem.

My car has 77000 miles.
My car has an automatic transmission.

A: Hi there. If the idle control valve is good...

Hi there. If the idle control valve is good then the problem is typically caused by a vacuum leak or an issue with the throttle body. I usually check the engine for vacuum leaks first. It may be a vacuum leak in one of the hoses or in the intake manifold. The intake gasket is a common failure.

If there are no vacuum leaks, then I would test the throttle position sensor to make sure it is reading correctly. If it is also reading fine, then I would check the throttle body itself. If the bore or plate is worn then this will occur. If you want to have this low idle problem inspected, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair this.

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