RPM increasing after releasing throttle

[Leviathan888]

I've seen a couple threads online but not specifically this car and not a definitive answer. I drive the car relatively hard, been noticing strange throttle response for a while now. Driving last night it really got to me after doing a quick pull in 1st gear. I went to shift at around 5.5k RPM, got off the throttle and pushed in the clutch. As soon as the motor was free from the transmission, it climbed up to almost 6.5k rpm with zero throttle application before dropping back down. This makes shifting difficult because the throttle needs to be released much earlier in preparation to shift in order to have the RPM matched for the next gear.

Is this normal? I did replace the clutch and flywheel about 2 years ago but with an OEM dual mass flywheel and Luk clutch. Is it the turbo de-spooling? Strange fly-by-wire quirk of this car?

Ideally I'd like the RPM to drop as soon as throttle is released, at the same time clutch is depressed.

[Cyrik]

I won't claim to know the solution here (especially since I don't have a manual) but since our cars are not drive-by-cable the only thing I could see causing this is you have a bad/dirty throttle body causing it to lag somewhat or you have a vacuum leak somewhere. Just spit-balling here. Do you have any codes?

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[bakedziti]

My old B8 A4 did this once but it was always at stop lights and it was the PCV which had gone bad. A quick swap and I was back in business. Once at a stop the RPMs would climb to about 4.5K IIRC, definitely not at high as 6.5k from what I recall, but it would do this on it's own once I was off the gas and on the clutch. I don’t recall any MILs or soft codes being tied to it but I could be wrong as it was 7 or 8 years ago now. Just a thought, could be way off base.

[Jayz691]

I'd be thinking vac leak. Have you looked at any data? Check your idle LTFT's. Could clear codes, and watch fuel trims. See if ECU is compensating for unmetered air.

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[a4audi4fun]

I had this problem on my B7 - does your cruise control work at all? That's an indicator of a faulty clutch switch. Once I replaced my clutch switch everything was back to normal.

[Leviathan888]

Cruise control works just fine so I’m not suspecting of the clutch switch. I’ll start with PCV and finding vacuum leaks. Would leaks be found on hoses or the main valve?