Revs Drop Slow

[40valve]

I actually don't mind it for stop and go traffic to work and back.

[earnhardtJR]

Sorry to revive this old thread.... did anyone find a solution to this problem, or is it just considered normal?

I have a CPO 2004 S4 with a manual, but even with it being under warranty, there is no way I am going to take it to the dealer and have them take 2 days to diagnosis it as "normal". Here are all the symptoms; I think they are all related:

1. CEL has come on and gone off twice in the past year (for about 2 days at a time). Both times, the dealer hasn't been able to do anything because the light went off by the time the dealer has seen it. Scanning the computer revealed a "lean condition", most likely caused by the MAF going bad (per the dealer).
2. When the motor is cold, the RPMs don't stick when I let out the clutch; they fall immediately and the shifts are smooth. When the motor heats up, then the RPMs hang when I let the clutch in for 1-2 seconds, especially at RPMs under 2.5k.
3. With a warm motor, the throttle response is bad (sort of like the engine is bogging). Shifts are impossible to get smooth- if I shift too fast, the RPMs are too high and the car surges when I let the clutch out. When I hit the unresponsive gas pedal, there is about a 0.5 second lag before the revs come up. So the shifts are basically like this- accelerate, clutch in, rpm's hang, next gear, clutch out, surge because the high rpm's, bog because of sluggish gas pedal, repeat. Not very fun to drive. Sometimes this bogging is worse than other times.
4. Sometimes if I take off from a slow roll in second gear (possibly other gears as well, but most obvious in second because of the steeper gear ratio), the motor feels like it is chugging to go from about 1k rpm until 2k rpm. After that, the motor runs smoothly.
5. Motor sometimes idles rough for about 2 seconds when sitting at a light. Revs drop by about 50 rpm, and the car shakes ever so slightly. Then the revs come back to normal and idles smoothly.

I am thinking this is a MAF problem. If something is going wrong with it, the problem will be most apparent when there is only small amounts of air flowing past it (which happens at very slight throttle openings). Maybe I am just trying to convince myself that this is the problem, but I can rationalize how every one of the problems above could be caused by a bad MAF. I am going to do the 55k service this weekend, and possibly change the MAF as well too see if the problem gets resolved.

Did anyone figure out what was going on with their own issues? Any remedies before I start replacing everything on the car?

[S4DTM]

Sounds like Throttle Body...I'm having the same problem and after VAGing it myself and having the dealer check it out, it was determined my throttle body is going bad. I'm working with AOA and the dealer right now to try to get it replaced...but we'll see. Good luck man

[earnhardtJR]

Sounds like Throttle Body...I'm having the same problem and after VAGing it myself and having the dealer check it out, it was determined my throttle body is going bad. I'm working with AOA and the dealer right now to try to get it replaced...but we'll see. Good luck man

Bummer... the fact that it is an intermittent problem on my car means that there is NO way the dealer will fix it. They will just give me the old "we never saw the problem while we had the car" line. When I had the starter going bad in my car (when the car won't even turn over for cold starts), I left it with the dealer for 2 weeks only for them to tell me that the car started fine every day. The week that I got the car back, it wouldn't start 5 out of 7 days.

Please let me know you get your problem resolved! If it turns out to be the throttle body, at least I can approach the dealer and use your case as by basis for diagnosing the problem with my car. Thanks!

[GotRS?]

Intreresting post. I've noticed pretty much all cars now have this issue to a various level. When I complained about this over ten years ago about my then new car, it was explained as "the new emissions requirement" where the engine needed to have more gradual off-throttle change.
It's a common issue, and the B7 A4 series has a weird way of lifting the revs up when you let off, you can experience that on a dyno at the end of a pull, I've seen them rev right up again.
My son's car (not Audi) has recently been used by an ECU tuner to investigate removing the serious hang on that model.