Engine RPM oscillates/fluxuates after cold start

[lebe0024]

When I cold start my car, the engine idles high around 2000 or so (like normal). Then after a minute or so the RPMs start dropping to 1000 then climb back to 2000. It does this for a couple minutes until the car warms up. Each climb sequence takes about 2 seconds. So the sequence is:

1. start car
2. idle at 2000 for a minute or so
3. quickly drops to 1000, then climbs from 1000 rpm to 2000 rpm over 2 seconds
4. repeat step 3 until car is warm. idles at normal low speed.

It's a 2003 Corolla CE and I don't have any engine/warning lights on. I don't experience any other problems driving the car. Is this what they call idle hunting? I thought it might be related to the TSB about the intake manifold gasket, but that TSB seems to say your MIL will come on.
Cold weather idling issue: Tach bounces up and down

Any help is appreciated!

[dorman68]

Sounds like an intake manifold gasket, fairly common issue on the 9th gen 1zzfe Corollas. The rubber gasket shrinks when it's cold and causes a vacuum leak, as the engine warms up the gasket expands and the vacuum leaks go away. A fairly easy DIY fix, the gasket is about $10.00. I have helped a couple of people with this fix. Hope this helps.

[Bucker]

MIL light will eventually come on if it is the intake manifold gasket. My car experienced idle hunting for 3 winters before MIL came on. And yes it was the gasket that doesn't cost $10.

[atifkm]

Originally Posted by dorman68

Sounds like an intake manifold gasket, fairly common issue on the 9th gen 1zzfe Corollas. The rubber gasket shrinks when it's cold and causes a vacuum leak, as the engine warms up the gasket expands and the vacuum leaks go away. A fairly easy DIY fix, the gasket is about $10.00. I have helped a couple of people with this fix. Hope this helps.

Where is the intake manifold located. Is it a small job. Does it requires anything else than gasket.

[Bucker]

TSB link below will show you where it isand what it takes to replace:

http://ww2.justanswer.com/uploads/sk...rolla_0171.pdf

[tarbasd]

Can't you get away from draining the coolant? Because that makes it more expensive, if you don't want to reuse the same coolant.

[mikered30]

Originally Posted by tarbasd

Can't you get away from draining the coolant? Because that makes it more expensive, if you don't want to reuse the same coolant.

If you change it while the car is cold you do not have to remove the coolant lines, just remove the throttle body from the intake manifold. You will need another throttle body gasket as they are not reusable.

[tarbasd]

I see. I think I'll have to do this soon. I have some minor fluctuation of idle speed when it is cold outside (<35), but it hasn't occurred to me until this last cold wave that it can be a malfunction. It had never really gotten cold here in SC, but I'm moving to Kentucky next fall.

[lebe0024]

Great! Thanks for all your help guys. A couple more questions:

1. How can I tell if my engine is a 1ZZ-FE?
2. What is involved in replacing your coolant? Do you know how to dispose of the old stuff?