Hello

I have a 2004 Sunfire.
I want to change the IAC because I have intermittent irratic idle.

Where exactly is it located and how much does it cost..?

Thanks

Walt

I'm not sure on the cost factor, but the intake system is on the front on the Ecotec, so access should be fairly easy. If it's anything like most other electronic components, I wouldn't expect it to be especially cheap to replace though.

As for the erratic idle, does it want to idle at different speeds, or does it just seem to get rough at times? Small amounts of moisture in the fuel can cause engines with multi-port injection to idle strangely, as can incorrect fuel pressure (potentially caused by a restrictive fuel filter). On my brother's Ecotec, we had this happening occasionally, and the problem seemed to correct itself after we changed the fuel filter. With your low mileage, I'd be a bit surprised at the fuel filter needing changing, but it really depends on where you get your gas, and how well they filter it before it gets into your tank. I once had a fuel filter plug up solid from one "dirty" tank of gas. It's not as common these days, but probably not impossible. I've had pretty good luck over the past few years by sticking mostly to name brand stations.

Although I'm not entirely fond of running ethanol in the gas, it does have the ability to help "dry" the system out if it's contaminated with water. Assuming you're in Canada, I know for sure that Shell, Sunoco, and Petro Canada definitely have ethanol blended into their regular grades. Keeping the tank as full as practical during the cooler seasons can help reduce the amount of condensation that can get in there too, especially if you don't put too much mileage on regularly. At least the prices are getting more reasonable lately to do this - compared to last summer!

If you want more specific instructions on replacement of the valve, let me know and I'll look it up in my service manual.
John

Hey John

Thanks for the input. I have a similar situation as some other posts I've read on this site.
Occasionally, on deceleration, my idle will drop to around 500-600 rpm for a couple of seconds then return to normal. i.e. approx, 900 rpm
A couple times, my idle went up to 1200-1300 rpm for 5 or 6 seconds then returned to normal. Mostly though, the idle drops, then returns to normal.
Strangely enough, this happens more frequently when there are rapid weather changes. i.e. It;s cool one day, then its warms up considerably the next day.
If you could give me a brief description from your manual on how to change the IAC, it would be appreciated.

Thanks
Walt from Toronto

Hi Walt,
I see we're actually not too far from each other - I'm in St. Catharines, and work in Burlington. That's the stretch of road that my car is most familiar with.

Does you car have a manual transmission? If so, then some of this behaviour doesn't seem too unusual. If I depress the clutch pedal a "little late" when decelerating, the car will pick up the RPM to around 1200-1300 also for several seconds, before eventually returning to "normal". It's done this since new. The fact that you notice the idle drop after changes in temperature would still lead me to believe that it may be condensation related. Try the gas as I mentioned above, if you aren't already. If you park indoors, this could also add to the problem, when the car is exposed to rapid changes in temperature. I'd still park indoors when given the opportunity though...

If you're still interested:

To change the valve:
- remove the air cleaner outlet resonator (the air duct going to the throttle body). To do this you'll have to undo a couple of clamps, disconnect a rubber hose, and unplug the IAT sensor.
- disconnect the IAC valve harness and remove the IAC valve screw.
- remove the IAC valve and screw.
- if you end up reusing the original valve, make sure that the valve and sealing surfaces are very clean. if the area inside the throttle body appear to have a lot of deposits that you can't easily clean, then it should probably be removed for a proper cleaning - but that's another story!
- compare the distance between the tip of the pintle and the mounting flange of the old and new valves. Use light finger pressure to retract the pintle of the new valve to the same distance of the old.
- lubricate the seal on the new valve with engine oil
- install the new valve, which should also include a new screw. Tighten the screw and plug in the harness
- reinstall the air cleaner outlet resonator assembly
- turn the ignition ON, but don't start the car
- turn the ignition OFF for 10 seconds
- start the car normally and check for proper idle

Have you had the car since new, or is it a more recent acquisition? If this is a new development, first try changing gas stations, and if that makes no difference, then you're probably barking up the right tree. If the car is fairly "new" to you, then maybe you'll find that this is just a "quirk" that won't change no matter what. As long as it isn't stalling, I'd give it some time with different fuels and see what happens.
John

Hey John

Thanks for the instructions. Much appreciated.
My car is a 5 speed and I bought it new in Feb 2004. No AC.
The falling idle speed happens intermittently. I buy gas at various stations, usually Petrocanada or Canadian tire.
Even with the same gas in the tank (I fill up about once every 2 weeks) the idle can be OK for days, even weeks then act up now and then.

Thanks again for the advice. I'l be buying the IAC around the Christmas holidays and install it during my time off work.
I'll post here again with the results.

Walt