So lately whenever I let off the accelerator by either holding down the clutch or coasting in neutral the RPMs are dropping super low, frequently as low as 500. It normally never drops below 800 or so while driving or at idle. A lot of times it fluctuates from 600-800 while coasting in neutral. Any ideas what it could be? I tried listening for any vacuum leaks under the hood with the engine running but it's so loud under there I really couldn't decipher anything.. Thanks!

 

do you have any engine mods??? cam, heads etc...

 

I have no idea whats been done to your car but its similar to some idle problems I had when tuning. Try resetting your IAC and TPS. To do so, disconnect each electrical connector from the sensors, turn the key on (dont start) for 5 seconds or so, reconnect the sensors, then start the car.

Sometimes the IAC, and/or TPS tell the pcm slightly different signal than what it actually is. i.e. throttle closed but TPS reads 1% open. Resetting takes care of this.

 

try cleaning the IAT, and cleaning your maf.

 

I'm still learning this stuff, what/where is the IAT? I know what the maf sensor is.. What materials/process do u use to clean these?

 

I'm pretty sure my 02 ws6 has had a cam put in it before I bought it, don't know what it is though.. other than that Just LTs, ypipe,catback, 160 deg. t-stat, and an slp air lid. I've been using these mods for about 30k w/ no problems at all w/ the car till just now

 

check for obvious things first. maybe a plug wire is loose.

 

yea def. not that...

 

There's two clips on your throttle body. TPS and IAT. Here I made this for you.



Unscrew the IAC sensor (2 small star screws) and just use a rag to clean off the head of the sensor. It's just a black head that spins around. Make sure it's clean.

as for the MAF, take rubbing alcohol and a Q-tip and clean the screen off so there's no nastyness on it.

Hope this helps.

 

You're referring to the IAC, Idle Air Control. Technically, its an electric motor with feedback to the pcm, not just a sensor. Yes, continue with cleaning it. The IAT is the Intake Air Temperature sensor and thats located near the air filter. Similar abbreviations, very different items. Have you tried resetting them like I posted earlier?

 

blah blah blah, yes. I know what they are and what they do, I unfortunately always mix the "acronyms" up. The IAT is indeed on the airbox, my bad.

Either way, clean it. Ive seen the iac cause idle problems a million times over. Could try resetting the tps, too....

 

Sorry, wasnt attacking you. The OP said he was learning this stuff so I thought Id elaborate.

 

ok, just did the reset procedure, now the TCS OFF light is on, and when i push the TCS button the light on the button won't come and and the TCS OFF light on the dash stays lit. With the idle I now have the opposite problem. The car idles at about 1100 stationary in neutral, and when driving the rpms actually go up when I coast in neutral or push down on the clutch, and anytime I turn on the A/C the rpms go about 200 higher. What's the story here?

 

UPDATE: I turned the car off and back on and the TCS issue is fine and it's idling much more normally now. I took in on about 20 spins around the block and I noticed that when I rev up and throw it in neutral the RPMS don't fall very much below 800 (a tiny bit lower w/ the AC on), but when I simply hold down the clutch the RPMs fall as low as 500. They seem to improve when I let off the clutch with it in neutral and just continue to let it coast. Some type of clutch issue?

I opened up the resevoir under the hood and the fluid level was a little below the black ring. There was a little bit of sludgy buildup around the wall and a tiny bit floating in the fluid, but not bad. What are your thoughts guys? Thanks!

 

have you messed with the throttle body set screw at all?

 

Haven't touched anything under the hood that I can recall

 

i did notice that when I pulled off the harness plug for the IAC the little blue rubber grommet was folded over back on itself on one side. But the plug still goes all the way it and the black clip still snaps into place. Don't know if that's of any significance

 

I'm actually having a similar issue in my a4. LT's, EGR!, AIR!, But no other mods. I had this issue before and after installing new plugs and wires. I'm gonna try resetting like suggested.

*edit* Well that was easy. I should have tried that a long time ago. Hopefully that's all I need.