weird idle
 

Ok guys, I've just about exhausted all ideas I've had here. For the past month or so I've been fighting the crazy P0171 code. It has resulted in new, coils, plugs, wires, - cleaned the MAF sensor, checked and inspected the egr tube. Replaced the egr solenoid and valve. Replaced all vac lines and finally the fuel pressure regulator. And thank the maker, the light has been off for almost a week now. Before when it would go off it would re-appear the very next day, so after many frustrating failed attempts I'm somewhat optimistic that I've beaten the code. Oh yeah in case Bill reads this, the battery cables were inspected thoroughly. Was a small amount of corrosion on the floor board where the negative cable was grounded, but other than that the cables actually looked new (slid the rubber boot off and everything). Anyways code has been off, but throughout this entire ordeal I've been getting a weird idle. Its not consistant. Sometimes when I'm at a light the car will idle like a champ. Then other times the car will actually shake (kind of pulsate) a little at idle, like when I'm at a stop light. Thing is the RPMs never fluctuate. All the gauges read normal. In fact if it weren't for the car shakin you wouldn't know anything is wrong. This is actually getting to be more frustrating than the SES light, because with all the new parts I've been throwin at her the car runs better than it ever has. Fuel economy went from low 17's to high 19's and will break 23 on the highway. I just had the exhaust inspected today for leaks. I was told for an 11 year old car that the exhaust was holdin up pretty good and that there were no signs of leaking or cracks anywhere. So I'm curious to see what you guys think.

I'd check out your fuel filter and the injector O-rings.

Fuel filter was just changed earlier last year, you think it could have clogged or started to fail already? The O-rings also were changed earlier last year when I did my LIM gasket swap. Is there a way to test the filter? I kno u r supposed to spray carb cleaner around o-rings, but like I said the SES light went off. Guess I could change em just to be safe though.

Did you ever clean the throttle body? How about the idle air control?

Let's see cleaned the throttle body when I cleaned the MAF sensor. And if the IAC is the plug on the front of the throttle body, then yeah I cleaned that to. Didn't realize it was kinda spring loaded when I first took it off, but then I remembered a thread u commented on where you mentioned that it had to be tilted slightly clockwise or something and then lined up for reinstall.

That's the throttle position sensor your thinking off. The IAC is a plunger with a cone on the end, it open and closes like a choke. If it's dirty it will not close and you have a vacuum leak.

Ooh right right. So where is the IAC on these engines?

and what is the best way to clean the IAC, or would it be best to just get another one? only a little over 20 bucks at autozone.

The IAC is right by the TPS near the base of the throttle body. Take it out and clean the cone. Or replace, your choice. make sure the O ring is good, and the seat is also clean.

Gotcha I'll take care of that right after work. Any value in replacing the PCV valve as well?