Higher than normal Idle
 

In a nutshell

Problem
All problems are inconsistent
While in Vegas - High idle(not wandering) 1k, 1.5k or 2k RPM at times
Back in Reno - Idle dropping very low(200rpm)for a few seconds before returning to norm.
After ECU reset - Car ran fine for weeks
Now High idle problem is back

Steps already taken
New fuel
Reset ECU
Cleaned air filter
IAC Valve was cleaned(by me) about 2.5 years ago so I didn't think it would be the issue

Car Modifications(all mods are years old)
gutted up-pipe
3" TBE w/ high flow cat
COBB OTS stage 2 CA gas map(has been for years now with no issue)
K&N oiled air filter



Story in detail

About a month ago I drove down to Las Vegas and while I was down there my car started to act weird. While I would be sitting at a stop light my RPMs would be stuck at 1k or 1.5k or even almost 2k. It would not bounce around or fluctuate but I noticed it to be different at different times. Then I got a CEL and had Kragen check it. The code said what I already knew "idle higher than normal" or something like that.

Then the car started making a loud belt driven sound as if I had a supercharger on the car. It was easy to hear that this sound was coming from the A/C compressor. I could mess with the A/C knob and it would stop the sound some times. The sound would start on its own at random times yet the A/C works perfectly so I don't know why it would be making that sound. I couldn't do anything about the problem when I was down there so I ignored it and just drove easy until I got back home.

I assumed that I either got some bad gas during the trip or I needed to clean my air filter since I was in a massive wind/sand storm on my way to Vegas. I also thought that I might have gotten sand in parts of the A/C compressor and that could be causing the sound.

I got home, cleaned my air filter(it's a K&N oiled filter), cleaned all the sand out of the engine bay(all I could get out). The problem now was the opposite of what I was experiencing in Las Vegas. In Reno my RPMs would drop so low that I could barely hear that my car was running. The RPMs would drop really low for around 2 seconds and then come back up to normal. This would happen every time I would take my foot off the clutch to come to a stop.

I was out of ideas so I figured that the A/C compressor might be messing up the idle so I removed the A/C belt. The noise stopped but it had no effect on the idle problem. I have deemed this problem completely coincidental and unrelated to the idle. I unhooked the battery and reset the ECU. The car started up and has ran normally for weeks until today. The high idle problem has returned but is not as severe. A lot of threads point to the IAC valve which I have cleaned once before a few years ago, so I don't think that would be the issue. I have also read about the cruise control cable causing the high idle. I have yet to mess with that. Any other ideas about what could be wrong?

Thanks

Oily MAF?

Vacuum/air leak somewhere. Get out the can of carb cleaner and start spraying.

Can't hurt to flash back to stock BASE map and see what happens.

There was a cruise control clip that I got installed by the dealer...I don't remember if it was a recall or a "customer satisfaction program" TSB, but it was free. Was this applicable to your car too?

If it's been a few years, I don't think you can assume that you don't simply need to reclean the IAC Valve. Worth a shot anyway, right? Isn't there a seal or gasket on it that sometimes fails?

Whenever my car has had idle issues it was always related to aftermarket fuel injectors. I know you have stock injectors, but maybe they need cleaning. Or how about cleaning/replacing the fuel filter?

I didn't know I could clean the fuel filter. I have put 50k on the car and its now at 100k AFAIK the fuel filter has never been replaced. Cody - It probably would not hurt for me to clean the IAC again. The gasket is only a couple dollars. Where would I find out about this cruise cable clip?

I have a spare WRX fuel filter somewhere you can have at a reasonable price.

I don't actually know whether it can be cleaned either :lol:

On my car, I change the fuel filter every 60K as per the manual. It never seems to affect anything, which is a good sign. It's super easy on my car since it's under the hood. At some point they moved it to the tank though.

I would clean your Maf sensor.

Van will clean your MAF sensor. Hopefully that fixes it!

I will clean your Maf sensor, but you have to come over and pull weeds.

Are they the weeds that break off at the root or the weeds with needle spikes? Or the weeds with needle spikes that break off at the root?

Here's a post that contributes absolutely nothing to the thread:

I have this same problem, intermittently. Sometimes it is high, sometimes it is so low it almost dies. I always attributed it to my lack of a tune.

All of the above.
Another thing to check out is your Idle air controller if you have one.

I had a problem like that in Reno, my car would idle rough and drop below 500 rpm then shudder and pick back up. I switched from Chevron to Shell gas and the problem has gone away. I don't know if that will help you but its worth a try.

Have you messed with the adjuster on the throttle cable? I took some slack out of mine once, and when it got really warm I would suffer the same symptoms as you. I put a bit more slack back in the cable and it went away.

Check and clean the IAC valve.

Check for anything that may be intermittently binding your throttle and cable. Check for throttle sticking and maybe clean it. Maybe some sand is binding it up.

Look for an intermittent vacuum leak, but these are usually not intermittent.

What can I spray on the throttle body assembly to lube it up? I have wd40 but I don't want to mess something up worse. I will try to clean the IAC again today if I get a chance.

You should probably do best with some silicone grease?

Sorry to bump this up, I've been having the same high idle issues for a while now. It starts up when when the car is usually completely warmed up and only in stop-and-go traffic type situations, it usually likes to stay at around 1750 rpm and stays there. I cleaned the MAF sensor with CRC sensor cleaner and some q-tips, cleaned the IACV and replaced the gasket, neither of these seemed to work. I took it down to independent automotive and they couldn't replicate the issue. About how much slack should be in the throttle cable? I can push it down a little bit with my finger but it's not super loose or anything. Same with the cruise control cable.... What am I missing?

I guess I never came back and posted my resolution. My problem ended up being a really dirty MAF sensor.

Is your car stock?

No, probably should have posted that my bad, I have a VF39 with the necessary supporting mods