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Rough Idle In Cold Weather


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In cold weather, my 97 Lexus ES 300 will idle rough after traveling about 30 mph and then coming to a complete stop. The car will pulsate for a few seconds and then return to a normal idle. This only happens in real cold weather (28 degrees) and only during the first complete stop. The car starts fine, idles regular, and I also allow ten minutes for the car to warm up before driving.

Does anyone know what could be causing this problem? Any assistance is greatly appreciated b4 I take the car to the dealer. Thanks.

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could be lots of things, all associated to fuel air mixture and delivery:

-dirty idle air control assembly (prone to carbon build up),

-dirty throttle body or lazy trottle position sensor

-lazy O2 sensor sending wrong info ECU, takes a second or two for the ECU to

catch up to the fuel air mixture difference at stop.

-could be a faulty crank or cam sensor

-lazy MAF sensor

-fuel pressure sensor

no CEL, right?

the only true way to diagnose what is going on is to have a scan tool hooked up to the car at the time it actually pulsates. This way you/a trained mechanic can actually pinpoint what is happening and what may be causing the pulsation.


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