rpm fluctuation in morning

[alexdcosta]

I own a Corolla 2006 1.8 XLI. I have noticed that the RPM flucuates between 1700 and 1100 during first start in morning when the engine is cold. I dont push the gas pedal at all. I let the engine warm on its own. the temp outside is around 21 deg C. When the engine gets warmer after 5mts, then the RPM remains constant @ 1000.

Why is the random fluctuation happening @ first start ?

[tarbasd]

Most likely manifold gasket. Do a search, you will find tons of posts.

[TrdSpeed140]

possible leaking intake manifold gasket.

[dorman68]

Originally Posted by tarbasd

Most likely manifold gasket. Do a search, you will find tons of posts.

I agree, a very common failure.

[mikered30]

Does your engine have an Idle air control valve and what engine do you have? Most of the idle hunting with a leaky manifold gasket happens when it is very cold, not warm like where you live. I am not entirely convinced it is a bad gasket yet, and it usually that trips a CEL. There is a TSB for this issue, but it is for US corollas. Has this happened since new? Spray carb cleaner around the intake manifold gasket when the engine is running and listen for a surge in RPM.

[TrdSpeed140]

I'd also like to know how fast the RPMs are fluctuating. for instance, does the rpm go from 1100 to 1700 in a matter of a second or two? or is it even more gradual or is it faster than that?