RS4 Idle issues

[scmguru]

Drove home from work today, about 40 minutes in stop and go with a couple of good full throttle runs..

I parked and noticed that my idle seemed to be oscillating by about 50RPM up and down.

Turned off the A/C.. same behavior.

Gave her a bit of gas, RPM's went up and then dropped about 200-250 below normal idle RPM (seemed like she was going to stall) and then went back up to normal idle, but still have the RPM oscillation..


Car has <9k miles and I've always used "top tier" fuel with the Audi fuel treatment every few of weeks or so.

Anyone ever see this? I didn't see a MIL or any kind of warning light.

[BLopes07]

Same thing happened to my car. But my b7 a4 u prob have an air leak on mine it was the pcv. Simple and easy install and cheap and my car would rev over the usual then go down and up and just when the car is about to stall it goes up again. The best way is take it to a shop and preform an air leak test. Hope this gives u sort off a good idea

[koolade9]

yup, vacuum leak... has the exhaust ever been off the car? Check the two rear vacuum lines...

[scmguru]

Exhaust has never been off of the car..S mode doesnt make it worse.. the RPM drop below normal idle after tapping the gas pedal is most pronounced with the clutch out in neutral if that helps?

[ArthurPE]

Exhaust has never been off of the car..S mode doesnt make it worse.. the RPM drop below normal idle after tapping the gas pedal is most pronounced with the clutch out in neutral if that helps?

is your crusie control working?
do the revs hang up (not drop fast) when shifting?
does the car start normally? (twist and release key, cranks until starts)

[jfunkey]

Exhaust has never been off of the car..S mode doesnt make it worse.. the RPM drop below normal idle after tapping the gas pedal is most pronounced with the clutch out in neutral if that helps?

with the car off unplug your MAF.. then go do it again.. See if that makes it better.. If not in a good change your getting a vac leak

[scmguru]

How do I get the plug off the MAF... most of the other plugs have a push button to release them.. MAF plug is different.. would rather not break it.

Also, will this throw a DTC/MIL that I'll need to have reset by the dealer?

[scmguru]

Arthur, Revs do hang up.. (not drop fast when shifting)

[Shomegrown]

is your crusie control working?

All modern Audis are DBW. Are you really suggesting there is a vacuum diaphragm running the cruise control? Think for a second.

[JimmyBones]

How do I get the plug off the MAF... most of the other plugs have a push button to release them.. MAF plug is different.. would rather not break it.

Also, will this throw a DTC/MIL that I'll need to have reset by the dealer?

The MAF plug should be like the other ones that Audi uses but if I remember right it is turned around when looking at it from the front of the engine so the release tab will be on the back. Yeah it will throw a check engine light if the engine is running without the MAF plugged in.

I would try disconnecting both battery cables and touching them together for a five seconds then reconnect to the battery. Don't touch the two points of the battery together unless you like being electrically fried because 450+ Amps is enough to kill you easily. We call this battery vu du at work and it has fixed a bunch of cars since the ECM has to actually readapt the values internally. After you do that you will need to reset the clock/date, one touch window feature, and steering angle sensor. (to reset the steering angle sensor take a few turns and the ESP light will turn off) The radio should still work because you have a B7 but it may also be a good idea to see if the radio code is in the owner's manual somewhere before hand.

[Covkiller]

Hi Scmguru
I have the same issue. Did you ever resolve your issue?

[dtrizzo]

Hi Scmguru
I have the same issue. Did you ever resolve your issue?

Curious how this turned out. Every once in a while I get abnormal revs when in Idle...