Friend of mine recently bought a nice 2001 coupe. He's doing a really good job of restoring it. I've been helping with stuff I have dealt with over the years. Flippy headlights, melted DRLs, fried EBCM, window regulator etc.

He's got one I've never had or heard of. On a few occasions engine unexpectedly revs up. I heard it happen once He had just put it in park (yes, its an A4) in my drive way. I thought he was just gunning it up for fun. He said no, didn't touch the gas.

He told me today it did same thing. His foot on the brake and in gear and in traffic and was pulling against the brakes Said it went back to idle pretty quickly. Sounds dangerous to me.

Has anyone heard of a problem like this and what might be the fix?

Are C5's accelerator by cable or by wire? Haven't seen an authoritative answer to that.

Thanks for any help and advice.

 

Have never heard of this one either. I had a throttle position sensor go bad but the throttle had no response what so ever. Wonder if it could have an opposite failure as well? Be interesting to hear the fix.

 

I keep asking if it's not being use to the small space between brake and accelerator and accidentaly hitting gas. I drove it and had no problems.

 

You may be right. I've never heard of this before.

Since it's drive by wire, any failure of the electronics should result in reduction/loss of throttle pedal response and error codes on the DIC.

Maybe there is something mechanically wrong with the throttle pedal assembly. Maybe it was removed and not re-installed properly.

 

Never heard of that problem either. Will be interesting to hear what he eventually find out.

 

Make sure your floor mats are not getting jammed underneath.

 

Or a decent sized vacuum leak/dirty throttle body. I would check fuel trims while idling to see if it's lean or something.

 

LMAO!! There was a very similar post on this VERY TOPIC several months ago. Many of us SPENT HOURS & HOURS trying to figure out how this could happen to a Fly By Wire System.

The OP spent hundreds of dollars on parts and NUMEROUS hours troubleshooting.

NOTE! The signals that control the Throttle have an A side and B side (PHASE) The A signal voltage is 180 degrees out of phase from the B signal voltage. The TAC MODULE and the PCM carefully monitor this OUT OF PHASE condition and IF, there is ANYTHING that does not match what the PCM expects the throttle or the accelerator peddle to be, the PCM will put the engine into REDUCED POWER MODE!


When its in REDUCED POWER MODE the accelerator peddle will NOT respond to anything that you do to it and the Throttle motor locks the throttle blade in the last known good idle position. Your lucky to be able to LIMP down the side of the road to a pull off location.

SO,, all that being said,, The OP of that Post up-dated the post saying that; (paraphrased) After all the troubleshooting and parts I think my BIG FEET was accidently pressing the accelerator sometimes when I was pressing the brake!




HOWEVER,,, ALL THAT BEING SAID,,, IF,, Unmetered air is getting into the engine via a VACUUM LEAK, it can cause the idle to raise. That was/is the very first thing that came to mind when I read this post.

Check ALl the vacuum lines and anywhere that un metered air can get into the intake manifold.

BC

 

Ha! I beat BC to the punch!

 

Previous Owner had installed an after market air intake like this. Any thoughts on that?

 

Wouldn't an un metered air leak cause a problem all the time? His problem seems very intermittent.

 

He is getting persistent P0332 code - Rear Knock Sensor with check engine. His mechanic replaced knock sensor and pigtail. Still getting code.

Occurs on hard acceleration always shows as (H)istory when codes are pulled. Don't think that could be related subject of this thread "unexpected accelleration". But who knows? When I've driven and rode in car it seems fine maybe stronger than my 2004. Haven't put them side by side.

Wondering if PO did some kind of crazy tune. advancing timing, etc. I don't have tools or knowledge to help him determine that.