Just started happening, a little worse in closed loop. No visible signs of vacum leaks. Could it be the intake? I put it back on about 2 months ago and no problems since. Thermostats been out but getting colder now so I'm putting it back in later today.

 

How high is your tach reading?

 

upwards of 1300

 

Tachs usually read a couple hundred high, but 1300 on an A4 is too high. You might want to check out Shbox.com to see how to check the IAC for proper resistance. Perhaps you boogered it while removing the intake or something like that. Make sure your plenum to the TB is on all the way around---not that it should cause a high idle, however it happens often that they don't go back on easily and you can't tell from looking at them from above. Again, I doubt that it woud cause a high idle.

 

maf, iac or o2. need to scan.
but now the trans is acting up
after replacing thermo, idle
is still up. injectors are holding.
doesn't disconnecting bat
reset???

 

Personally I'd start with the basic "spray the engine down with carb cleaner" approach and see if you can find any vacuum leaks, I've seen weird idle problems both high and low related to vacuum issues. Can you think of any other issues you're having aside from idle?

Also there's a procedure to reset the IAC, please see Shoebox's page http://shbox.com/1/4th_gen_tech2.html#iac_reset

Hope that helps =)

 

Disconnecting the battery resets the long term fuel corrections. It there is no "learned" idle setting. This is a programmed value - stock is 550 in gear, 650 in neutral for the A4. There is a learned IAC preset position, and Shoebox's page explains how to reset that. Check your coolant temp sensor reading (the one in the water pump housing that feeds the PCM). The PCM elevates the idle rpm when the engine is cold.

 

did the iac reset according to shbox and it did not alleviate the problem
sprayed with starter fluid - i know i know but it was all i had on hand
unplugged the maf and drove around with no noticeable change. unplugged
the iac and nothing. egr was disabled and ports blocked off a few months ago when doing the headgasket. SES light remains on as does security.
abs inop comes on too. i did find a broken vac line, far left side way back in the corner by the hood hinge. connected with a piece of vac hose and
the idle went down a tad.
pretty sure the intake is ok as far as leaks and the computer is ok too.
i suspect the maf. if so what codes would it throw?
drives good, pulls hard, lays down the rubber no prob but smells of fuel
when idling. i have not ohmed anything yet. i do not have a scanner so worse comes to worse i'll stop by autozone to retrieve. this is about all i can think of boys. help me with your thoughts on this one

 

just a quick update but I found that the air pump fuse is blowing. even blew a 30 amp. related to the high idle?
also ohmed the iac and nothing between c and d. I'll be replacing it.

 

The AIR pump fuse usually blows because the pump rusts and siezes up. Since the AIR pump does not operate except for a couple minutes at startup to help the cat(s) heat up, it has nothing to do with the idle, and an idle problem will not affect the pump. Unplug the AIR pump, and put a good fuse in the circuit, and that will eliminate DTC 29.

You indicate that when you pulled the IAC connector, nothing happened. Try this - with the IAC connector connected, turn the A/C on or turn the steering to put a load on the engine. Does the engine idle speed change? IF it does, the IAC is not working. If it doesn't change, the IAC is working, responding to the added engine load to keep the RPM constant.

An easy way to verify the IAC motor function is to watch it on a scanner. The counts should be down to "0" if the idle is at 1300 and its won't come down.

The engine can't idle high without extra air. It's got to be getting the air from somewhere. Is it possible the throttle linkage is preventing the throttle blades from closing all the way?

 

Ok, concerning the scanner that was going to be my next question. I have a laptop and might as well take the plunge so what do I need in the way of cables and software? A little research revealed that OBD I is cheap for the setup. Besides, after I get everything buttoned up, I want to go with an email tune preferably through madz.

Linkage appears to be ok. Even backed off the screw and no change.

And I'll try the IAC test in a bit and update.

Just when I thought this beast was under control

 

Free downloads of the software:

http://www.ttspowersystems.com/
(DataMaster free use is limited to 20 data logs. Then you have to pay for a license).

http://www.andywhittaker.com/

Cable:

http://www.akmcables.com/

Understanding the data:

http://www.injuneer.com/ScanMast.html

 

thanks

and I did IAC test you mentioned and the idle did not go down at all

 

Not to hijack the thread, but I am also trying to figure out my high idle. Fred, I tried this, and the idle speed went from my constant 1150 to about 1000 when I turned the wheel, then went back up to 1150 when I stopped. Is this normal operation of the IAC? BTW, this is the stock IAC from my 48mm TB. Thanks.

 

As mentioned, the Tach usually reads high, so 1150 with an M6 might only be around 950+-, which sounds right. JMHO