Unexpected Unexplained Engine Revving
Thread Starter
Pro
Joined: Jun 2007
Posts: 647
Likes: 135
From: Big Canoe Georgia
Unexpected Unexplained Engine Revving
Folks, I have encountered an unusual car behavior a few times recently. This is the scenario:
I start my car in the garage and after a few seconds I start to back out. My clutch was already fully engaged to start the car and to move backwards I put the stick into reverse, start to start slowly disengage the clutch, and add a little throttle. I'm now moving backwards about 2-3 miles per hour, all is good. When I get about two car lengths back from where I started I want to prepare to go forward. I fully engage the clutch and remove my foot from the throttle and then it gets weird. The engine accelerates up to three thousand rpm's and a few seconds and then falls back to normal idle speed. When the engine started to accelerate on it's own I was not on the throttle at all. I only recall this happening the first time I back my car out for the day. Thoughts? Does the engine temperature play a role here?
I start my car in the garage and after a few seconds I start to back out. My clutch was already fully engaged to start the car and to move backwards I put the stick into reverse, start to start slowly disengage the clutch, and add a little throttle. I'm now moving backwards about 2-3 miles per hour, all is good. When I get about two car lengths back from where I started I want to prepare to go forward. I fully engage the clutch and remove my foot from the throttle and then it gets weird. The engine accelerates up to three thousand rpm's and a few seconds and then falls back to normal idle speed. When the engine started to accelerate on it's own I was not on the throttle at all. I only recall this happening the first time I back my car out for the day. Thoughts? Does the engine temperature play a role here?
Drifting
Joined: Oct 2011
Posts: 1,872
Likes: 333
From: Olmsted Falls Ohio
St. Jude Donor '12 thru '24
OP, do you have an aftermarket throttle body on the car? I had the same issue with an aftermarket throttle body, re-installed the OEM throttle body and no problem since.
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Le Mans Master
Joined: Aug 2015
Posts: 6,884
Likes: 2,884
From: Toronto
Does it happen once you drive around and park somewhere and shut the car off. Then come back and pull out of the parking space? This could rule out the throttle position sensor (which usually throws a code). Another long shot... try disconnecting the battery to reset the electronics and/or look at the MAF sensor. Start with the easy little things. Good luck.
Thread Starter
Pro
Joined: Jun 2007
Posts: 647
Likes: 135
From: Big Canoe Georgia
No, this has only happened when I first back out of the garage. It happens when I put the clutch back in during the 20 feet of backing up. This probably only happens once a month or less. I drive it every day. I did see someone with an A8 in this thread have a similar experience so that might rule out rev matching. I would not want to disconnect the battery unless I had other issues.
Pro
Joined: Apr 2008
Posts: 586
Likes: 119
From: Saint Cloud, FL
Happened to me yesterday when leaving the office. For me it happens when clutch is disengaged and you barely tap the gas. For me it only appears to happen during a cold start some small (I've not measured) amount of time after the cold start.
Instructor
Joined: Apr 2014
Posts: 244
Likes: 11
has anyone figured out what causes this?
Last edited by Edmlaser; Jul 21, 2023 at 09:08 PM.
Instructor
Joined: Apr 2014
Posts: 244
Likes: 11
first time it happened I thought maybe Rev match. I was thinking maybe I accidentally turned ot on or something.
second time, i know it wasn't on.
cranked, released parking brake, put in reverse, started to apply a little throttle to let the clutch out, and it revs up on its own....both times.
I don't know if it would settle down on its own, because both times I give the throttle a quick kick and it settles down to normal idle.
second time, i know it wasn't on.
cranked, released parking brake, put in reverse, started to apply a little throttle to let the clutch out, and it revs up on its own....both times.
I don't know if it would settle down on its own, because both times I give the throttle a quick kick and it settles down to normal idle.
Instructor
Joined: Jul 2019
Posts: 190
Likes: 84
From: Tucson AZ
Possible ECM Learning curve. Suggest to make sure Battery is in good shape, then disconnect Battery for 10 minutes or so then start and idle for a few minutes then drive normally till fully warm.
Instructor
Joined: Aug 2021
Posts: 149
Likes: 88
From: Hazel Green, AL
Have experienced the same symptoms a few times; it always happened after a cold start while backing out of the garage. The fix has been to simply let the fast idle settle down before backing out. Just talking about 10 or so more seconds, not a minute
Instructor
Joined: Oct 2022
Posts: 213
Likes: 58
Anyone have this figured out? Mine does the same thing after a cold start every once in a while. Put in reverse, when letting clutch out and tapping the gas the engine over revs. This behavior goes away after about 10 seconds… just as you described.