Idle rev issue- No solution yet...

Ive never been known to turn on the A/C. But the other day in 100+ degree sun i caved in and finally pushed the A/C button for the first time for the season. The idle was higher since the A/C was on and thought nothing of it since that happens with probably every car on the road in some form or another. Like i sad thought nothing of it until the A/C button was off the next day and the engine isn't idling normally..:confused:
Typically the engine is reving inconsistently between 1300-2000 rpm. Not noticeable on highways but can get really annoying at stop lights. The typical downshift clunk is noticeably louder now that the engine isn't idling properly which is also a concern. I looked at typical idle issues/solutions on the forums and none that i have tried have done nothin. This is something that i feel shouldn't just be ignored although im assuming/hoping it will resolve on its own.. 7 days have passed so far and no luck yet... no CEL or codes thrown my way, although this is the only situation that i would like to see the CEL for some direction/ indication...
Any help or input is greatly appreciated! A/C related, who knows! Just thought A/C being used may be worth mentioning.

Here is what i have replaced/done:
-Unplugged the battery to reset any potential issues... made sure leads were solid when i plugged the battery back in.
-Replaced TPS (throttle position sensor)
-Replace Fuel Filter
-Replaced PCV Valve
-Put fuel system cleaner in the tank so we'll see if that will resolve anything (i have my doubts) it cant hurt though...
-Replaced the battery
-Cleaned the IAC (no luck)
-Replaced the Fuel pressure regulator (Still so freaking luck!)

Here is what ive read for solutions but NOTdone:
-Replace the IAC (idle air control valve)
-Unplug the power steering sending unit. $200+ for a replace!?!?!?
-check for intake manifold leak with carb cleaner or easy start?
Im starting to think is some tiny vacuum leak or a crack on the inside of the intake manifold gasket! This is gonna be a lame weekend...


Thanks in advance!

UPDATE UPDATE UPDATE! SOLUTION FOUND:
The problem was the combination of a cracked intake gasket AND a failed IAC valve! Replacing the gasket was a pig of a job! The collet for the EGR pipe was locked on the lower manifold! I ended up taking the hack saw to it to finally get it off. It took a ton of penetrating oil and my whole body weight to break it loose! After i retrieved the other half ot the EGR tube i had someone weld the tube back together for reinstallation! What a mess! Rebuilt and reinstalled the manifold and torqued it down to 13ft lbs as specified on the forums. After that and first start of the key it started right up, although the idle was slighlty higher than 1000RPM, but much better than close to 2000RPM as before. The idle was fluctuating slightly as well Grrrrrrr!, i let the engine get to temp and shut it off. I unboxed the IAC and slapped it in and made the final difference! Phew! Im now idling at a steady 750RPM and much less stressed! Thanks to all who helped!!! Pictures to come of the job once i find out how to post pictures!

Sounds like you have a pretty good idea where to continue troubleshooting. I would start by pulling the IAC to clean it and check its functionality. The plunger will cycle open/close when you turn the ignition. Then you'll know if it's worth replacing the IAC or moving on to the next thing.

Good luck and hope for cooler days before our entire state burns to the ground. :(

Sounds like the fuel pressure regulator to me. Same symptoms. Did it on my previous VX. Not a difficult job. Fixed the issue.

I sure hope so! BTW VXorado I saw your car the other day (6-22-12) in Denver. Had to stop and take a picture! Sweet ride! Hope to see you around!

UPDATE UPDATE UPDATE! SOLUTION FOUND:
The problem was the combination of a cracked intake gasket AND a failed IAC valve! Replacing the gasket was a pig of a job! The collet for the EGR pipe was locked on the lower manifold! I ended up taking the hack saw to it to finally get it off. It took a ton of penetrating oil and my whole body weight to break it loose! After i retrieved the other half ot the EGR tube i had someone weld the tube back together for reinstallation! What a mess! Rebuilt and reinstalled the manifold and torqued it down to 13ft lbs as specified on the forums. After that and first start of the key it started right up, although the idle was slighlty higher than 1000RPM, but much better than close to 2000RPM as before. The idle was fluctuating slightly as well, i let the engine get to temp and shut it off. I unboxed the IAC and slapped it in and made the final difference! Phew! Im now idling at a steady 750RPM and much less stressed! Thanks to all who helped!!!

Sweet. :thumbup:

I'm glad you were able to resolve the idle issue. Remember, open invitation to the meet next Sunday.

Excellent news. I may have to try both of those fixes soon. I've been getting a "cylinder three misfire" code lately, she's been tough to start, idles rough, and just the other day I got the high idle issue that went away after everything warmed up.

Did you get any codes? Like 171???

I was getting three other codes, but all of them delt with oxygen sensors. I can't remember all of them, but I was getting P1171 (Fuel System Lean During Acceleration), P03something, and P05 or 7-something. All of those went away when I did a thorough clean of the EGR and MAF sensor.

P0303 (cylinder three mis-fire) is sticking around, though. The code always seems to happen during a sustained idle and usually after the engine is up to operating temperature. She has a rough idle now, and from the research I have done here are some of the possible causes:

-Faulty spark plug or wire (don't have those, but haven't checked the wire leading to the coil pack yet)
-Faulty coil (pack) (have switched the coil packs and mis-fire stays at cylinder three)
-Faulty oxygen sensor(s) (haven't checked these yet, but figured that they would throw their own code)
-Faulty fuel injector (haven't checked this yet, and frankly don't know how to)
-Burned exhaust valve (man I hope not)
-Faulty catalytic converter(s) (possible, but "rotten egg smell" that is supposed to point to a bad cat isn't really present)
-Running out of fuel (tank is full)
-Poor compression (haven't checked this yet)
-Defective computer (wouldn't know how to check this)

I've also read on here that others have had similar problems and it was a bad intake manifold gasket. I got some starter fluid this morning that I will spray around the intake tomorrow to see if the idle changes any.

Any other suggestions would be most welcome.