Chev. malibu 3.1L idle

[mayo]

I have a 1998 chevrolet malibu 3.1l v6 with 45,000miles.When I first start it in the morning the idle goes back and forth from 1,000 to 1,400rpm for about 1min.Then it runs fine.It's not giving me any codes.could it be a sensor even if no codes show up or maybe just cleaning the air intake body would help?

 

[Terry]

My guess is a idle air control( IAC ) valve that is sticking and indeed needs to be cleaned or the plunger has been damaged or is not seating properly. Pull and inspect.

A real GM trained mechanic may pipe in here and help, I only play on on TV.

 

[T-Keith]

It's typical for most fuel injected engines to run at high idle for the first couple minutes. It gets things circulating, warms up the engine, and charges the battery.

-T

 

[mayo]

It's only started doing it the last couple of weeks.I also seems the idle is a little rough when warm also.

 

[Gary Allan]

I agree with Terry. The engine is "seeking" the proper idle speed and is having a hard time making the fine adjustment without over shooting, so it goes too high ..then compensates and goes too low.

 

[Drew99GT]

This may not be it at all, but you may want to check and make sure you do not have the dreaded intake manifold gasket leak. If it gets bad enough in the right spot, it will create a stubborn vacuum leak that is practically undetectable, and would perhaps create the symptoms you've described.

 

[mayo]

The intake gasket was changed 3 months ago.

 

[36coupe]

You may want to try a vacum gauge to test for leaks

 

[Jelly]

quote:

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Originally posted by mayo:
I have a 1998 chevrolet malibu 3.1l v6 with 45,000miles.When I first start it in the morning the idle goes back and forth from 1,000 to 1,400rpm for about 1min.Then it runs fine.It's not giving me any codes.could it be a sensor even if no codes show up or maybe just cleaning the air intake body would help?

---

I'd first suggest (especially since this is an OBDII vehicle) to hook it up to a scanner and see if any codes show up.

Over at the technical school the other day, I was messing around with a 3.1L with a high-idle...scanner showed high-voltage from the throttle position sensor.

New sensor, and the problem was fixed!

I'd figure it's either the IAC or TPS.

 

[mayo]

Thanks for the replys.
I'll give those ideas a try.

 

[mayo]

I check for a vacum leak and found none.Then I cleaned the IAC and the air intake and waited until the next morning and everything was fine.Thanks alot guys.