audi 80 revving up

Honest John Back Room » Technical matters
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Sun 28 Dec 2003 11:33
audi 80 revving up - esky365
I own a 1982 audi 80 and most times, but not all, when I use the clutch, the engine will rev up as soon as I put my foot on the clutch. No matter how gentle I am and I can actually feel the accelerator pull away from my foot. There is no entanglement between the clutch and throttle cable and the carb is well set up and smooth in operation, the car is running well perhaps a little on the lean side even. Any ideas?
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Sun 28 Dec 2003 22:12
audi 80 revving up - esky365
Anyone??
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Mon 29 Dec 2003 09:53
audi 80 revving up - Adam Going (Tune-Up)
I would say there HAS to be some interaction between clutch and throttle at some point. This could be a problem with the pedal hinges at the top of the pedal box, some flexing where the cables pass through the bulkhead, or under the bonnet. If (IF) my memory serves me correctly, the clutch cable should pass over the top of the air filter box intake section - I often find them left underneath, where it can cause the throttle cable to flex as clutch is actioned.

Really can't see any other explanation.

Regards, Adam
Whatever is rightly done, however humble, is noble.
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Mon 29 Dec 2003 19:21
audi 80 revving up - esky365
Thanks I will certainly have a look. I also forgot to mention that the revving up does not occur until you touch the accelerator, so you can have used the clutch with 30 secs between pressing the accelerator eg when turning a roundabout, and it revs up that bit later, but it is certainly weird feeling that accelerator moving away from you when you just touch it.
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Mon 29 Dec 2003 20:08
audi 80 revving up - Peter D
Ok you mention roundabouts as an example but does it do it in a straight line. I'm thinking fuel float level here, or thottle close damper. Come back. Regards Peter
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Tue 30 Dec 2003 09:27
audi 80 revving up - Mark (RLBS)
Its not as simple as your heel pushing the mat which is leaning on the accelerator ?
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Tue 30 Dec 2003 09:50
audi 80 revving up - esky365
The problem can occur at any time in any direction, not necesarily on a roundabout. Thanks for the mat idea, but I did look at that. The weirdest incident occurred when I was on a very steep incline in Lincoln and was going through a combination of road works and traffic lights and I found that while "balancing" the car for slow progression and on hill starts the engine would rev up and down. As you can imagine the balancing was not easy.
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Tue 30 Dec 2003 10:03
audi 80 revving up - Mark (RLBS)
Does it happen when you have a passenger ? The older Audis used to have the throttle linkage on a right hand drive car running across behind the console and pressure from a passenger's foot could affect it.
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Tue 30 Dec 2003 11:51
audi 80 revving up - esky365
Can happen at any time, but then again not. :)
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Tue 30 Dec 2003 20:46
audi 80 revving up - Peter D
Is this Carb mounted on a rubber anti vibration isolator and if so are you sure it has not split. Listen all around the area with a small diameter peice of tube and the other end stuck almost in you ear. Regards Peter
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Thu 1 Jan 2004 12:18
audi 80 revving up - esky365
Ok, thanks for all the contributions, it is time to get the sleeves rolled up and out into the sleet and start investigating. I will get bak to you WHEN I find the solution.
Thanks :)
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Fri 2 Jan 2004 17:32
audi 80 revving up - dieselhead
Just a thought.. it could be that the high vacuum in the inlet manifold at idle is partially opening the throttle..might be worth checking that the carb throttle plate return spring isn't weakened or incorrectly fitted.
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