I have a 1993 Buick LeSabre it has 207,000 miles on it uses no oil and the only major thing done to this car was a tranny rebuild last year.Sometimes when you start it the engine will rev up to about 3500 rpm and after it runs a little it usually will go back to normal by itself,the service engine light will come on and go off at different times,but if its really cold outside it will not come on,only if it's warm or humid does anyone know what the problem is,diagnostics show nothing.
Thanks
Brenda:)

Sounds like a ECT. Engine coolant temp sensor. I don't think it's seeing proper coolant readings by the ECM. It may be a bad sensor, or low coolant. When's the last time you gave it a good coolant flush? Is the bottle full?
How is the induction system? I bet that throttle body is all carboned up at that milage. Have that done if it hasn't.

Sounds like a ECT. Engine coolant temp sensor. I don't think it's seeing proper coolant readings by the ECM. It may be a bad sensor, or low coolant. When's the last time you gave it a good coolant flush? Is the bottle full?
How is the induction system? I bet that throttle body is all carboned up at that milage. Have that done if it hasn't.
Thanks,but had the system flushed last year and the throttle body cleaned,sometimes I think it's possessed.. lol... she isn't pretty to look at anymore but it's my pet taxi so doesn't matter... if it blew up today,I have gotten my moneys worth.. :D

I have a 1993 Buick LeSabre it has 207,000 miles on it uses no oil and the only major thing done to this car was a tranny rebuild last year.Sometimes when you start it the engine will rev up to about 3500 rpm and after it runs a little it usually will go back to normal by itself,the sevice engine light will come on and go off at different times,but if its really cold outside it will not come on,only if it's warm or humid does anyone know what the problem is,diagnostics show nothing.
Thanks
Brenda:)
This could also be caused by a sticking Idle Air Control Valve (IACV) sticking, or a Mass Air Flow Meter (MAF) that is out of range or it's sensing probe is contaminated.

You may want to check to see what codes may be stored.

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