97 Sunfire 2.2l rouge idle when cold

My 97 sunfire acts like it's missing on one cylinder when cold. It clears up after a few minutes. I've checked and found that it is acting up on one cylinder only. Replaced the plugs - no change. Tested compression on all cylinders and it's excellent. I'm puzzled now.

Anyone have an idea?

Clean your IAC valve. Ths does the job of the choke. They get really gummed up.

Clean your IAC valve. Ths does the job of the choke. They get really gummed up.

I knew before I opened this thread when I saw 'public' I was going to see IAC valve! And good too. check that and if after youve cleaned it it still is buggered. You may have dirty injectors- only if you get sputtering under hard acceleration. But IAC make most sense as it's when it's cold so that #1 on your list!

I knew before I opened this thread when I saw 'public' I was going to see IAC valve!

I guess I repeat myself too much (I am old). Perhaps I should find another way to fix this issue. Perhaps something like this.

A complete engine and fuel system rebuild should do it. Good Luck.

I guess I repeat myself too much (I am old). Perhaps I should find another way to fix this issue. Perhaps something like this.

A complete engine and fuel system rebuild should do it. Good Luck.

Sounds good!

Well, I did the unthinkable and took it into a GM shop. After 4 hours testing compression, plugs, wires, spark, vacuum leaks, injectors...they don't know precisely what is causing the problem but think it may be either a weak valve spring on cylinder 1 or a valve guide problem. I'm bring it back on Monday to finish the diagnosis and repair. Will post an update when I am told what it is.

It turned out that the problem was a broken valve spring. It broke in such a way that it couldn't turn in on itself and when the engine was cold it would run rough. As the engine heated up the metal expanded to the point that the valve would close correctly. They replaced the spring and the problem is gone. And my mileage has gotten much better.

Well, I did the unthinkable and took it into a GM shop. After 4 hours testing compression, plugs, wires, spark, vacuum leaks, injectors...they don't know precisely what is causing the problem but think it may be either a weak valve spring on cylinder 1 or a valve guide problem. I'm bring it back on Monday to finish the diagnosis and repair. Will post an update when I am told what it is.

It turned out that the problem was a broken valve spring. It broke in such a way that it couldn't turn in on itself and when the engine was cold it would run rough. As the engine heated up the metal expanded to the point that the valve would close correctly. They replaced the spring and the problem is gone. And my mileage has gotten much better.

Was it intake or exhaust?

Well, I did the unthinkable and took it into a GM shop. After 4 hours testing compression, plugs, wires, spark, vacuum leaks, injectors...they don't know precisely what is causing the problem but think it may be either a weak valve spring on cylinder 1 or a valve guide problem. I'm bring it back on Monday to finish the diagnosis and repair. Will post an update when I am told what it is.

I really don't see what's wrong with taking it into a GM shop. if I had to make the choice between me not knowing what I'm doing and taking it into someone who does... hell I'd take it in. It's not worth the x amount of dollars you'd end up spending if you ended up screwing up big time.

*tosses 2 pennies into the cavalier collection plate*

Broken valve spring. Couldn't you hear that? Those usually let the rocker arm bounce around enough to give you some tapping.