RS4 Tech Help - Jumpy Idle

[e36graduate]

Recently noticed at idle my rpm's jump up from about 900 to 1200 and back down - repeating (almost like my old e46 M3 did on cold starts). When I take off the oil cap their is a bit of vacuum and the car dies. If I take out the dip stick, the bouncing idle smooths out to almost a normal idle.

I vag checked the MAF on a 1st gear pull and seems in working order. I also unplugged the MAF and the idle still bounced.

I vag checked adaptive values while then bad idle was present and got:

Bank 2
Idle -1.5%
Partial -4.7%

Bank 1
Idle -2.3%
Partial 0.0%

I did see some misfires on initial cold start spread out to almost every cylinder. As soon as he idle came down to normal the misfires disappear.

I also noticed the other cold morning start the initial start up rpm was much higher than usual and then as it comes down it is a little rough.

Once I unplugged the dip stick and got the idle to smooth out, checked the trims and everything was smooth. Car ran much better, more power for last couple of days. Last night I noticed the bouncy idle was back.

Gut is telling me the oil separator, however wants some I out before I start trying to throw parts at her!

Also, do the intake runner flaps have anything to do with this phenomenon? I vag checked the runner plates and it showed position anywhere around 60 - 70% while spec calling for 0 or close, I assume? I have JHM tune with the flap error code eliminator so not sure if the flaps are a problem.

[komseh]

The runner flaps do help control idle and 60-70% is definitely out of spec. When I removed my flaps I experienced the same rough idle. I ended up having a few fouled fuel injectors.

The 0.0% long term fuel trim usually means there is something wrong with an o2 sensor unless you just reset your ECU(cleared codes).

[e36graduate]

Thanks... the idle is consistently jumping up and down like clock work.....up down up down up down - why would taking out the dip stick smooth this out? It's got to be something with the crankcase vent system......

no CEL codes either.

[Avussilver07]

Our B7 A4 was doing that same thing, idle jumping upand down. Felt like that 2.0t was a Chevy small block with a lumpy cam, I got no codes and it was the PCV breather. Picked up a new one from ECS Tuning and problem solved.

[ven0m]

Recently noticed at idle my rpm's jump up from about 900 to 1200 and back down - repeating (almost like my old e46 M3 did on cold starts). When I take off the oil cap their is a bit of vacuum and the car dies. If I take out the dip stick, the bouncing idle smooths out to almost a normal idle.

How many miles does the car have and was the PCV changed previously?
I was told that the if the engine stalls when you pull the oil cap, this indicates a bogged PCV. Does the car produce a lot of smoke when starting from a stand-still?