Audi a3 revving by itself

jaffa20

My fly by wire audi a3 has started to rev itself iwhen stopped in traffic. It normally just goes up and down between 1k and 2k but sometimes 3k. It can be annoying and i don't think it's serious because it doesn't happen all the time and settles down after a few revs when it does. Just wondering if you guys know what the problem could be and the cost involved here if it is a major problem

Thanks.

Lucifer

If its a 1.6 petrol there is a good chance it is the throttle body as I have heard that these give trouble. No idea how much they cost though as I have yet to fit one myself.

guerito

Sounds like a problem I had with my 1.6. When the engine warmed up the revs would jump when idling, sometimes cutting out too. Turned out it was the throttle body. No big deal to sort out. I had it taken out, cleaned and reset as part of a general service at my local indy garage. Can't remember exactly how much it cost, but it wasn't much at all, and she's running perfectly now.

Fundthementals

If its a TDI - could be releated to a faulty engine temperature sensor. Is the temp guage stable at 90 deg ? If its fluctuating from 0 -90 when the engine is at normal op temp, sensor output screws up the ecu fuel delivery calc.

crosstownk

Fundthementals wrote: »

If its a TDI - could be releated to a faulty engine temperature sensor. Is the temp guage stable at 90 deg ? If its fluctuating from 0 -90 when the engine is at normal op temp, sensor output screws up the ecu fuel delivery calc.

Be careful here - the temp sender sends two signals on separate wires - one to the ECU and one to the dash. Sometimes only one may be reading incorrectly. So if the dash is reading correctly it does not mean that the other temp signal is correct.

While the temperature sender could be the cause it does sound more like a dirty throttle body. Have the throttle body cleaned with some cat friendly carb cleaner and see what happens - it may sort it out. After cleaning the throttle body it may be necessary to reset the throttle angle which will require a diagnostic tool.

@OP - what engine size, fuel type and year is the A3?

jaffa20

guerito wrote: »

Sounds like a problem I had with my 1.6. When the engine warmed up the revs would jump when idling, sometimes cutting out too. Turned out it was the throttle body. No big deal to sort out. I had it taken out, cleaned and reset as part of a general service at my local indy garage. Can't remember exactly how much it cost, but it wasn't much at all, and she's running perfectly now.

Yeah that sounds exactly like it. Good to hear it's not too difficult to fix. Mine is a 1.6 and has been cutting out the odd time too and i thought it was my driving because i only bought it recently.

jaffa20

crosstownk wrote: »

Be careful here - the temp sender sends two signals on separate wires - one to the ECU and one to the dash. Sometimes only one may be reading incorrectly. So if the dash is reading correctly it does not mean that the other temp signal is correct.

While the temperature sender could be the cause it does sound more like a dirty throttle body. Have the throttle body cleaned with some cat friendly carb cleaner and see what happens - it may sort it out. After cleaning the throttle body it may be necessary to reset the throttle angle which will require a diagnostic tool.

@OP - what engine size, fuel type and year is the A3?

Thanks,it's 1.6, 01, petrol. That must be, i'll have it cleaned anyway and see what happens. Would it cause much problem driving it around in mean time?

crosstownk

jaffa20 wrote: »

Would it cause much problem driving it around in mean time?

Depends. See if the symptoms persist.

Tipsy Mac

Did you have the air con turned on when it was happening? This can cause revving.

unkel

Tipsy Mac wrote: »

Did you have the air con turned on when it was happening? This can cause revving.

Surely not to 2k or 3k rpm while stopped in traffic unless the outside temperature is >100 degrees centigrade?

My vote is on a dirty throttle body too. I had the exact same problem in the Rover 75 - the main dealer spent hours looking at it. Said they tried to clean / fix it but that I needed a new one. They didn't have it in stock and on my way home the problem was gone and it hasn't come back (now a year later)

Muckie

I'd clean the throttle body first and if that doesnt solve the problem,

i'd next guess it bein the engine temp sensor. Very similar problem happen

on my Subaru last year.

jaffa20

Doesn't seem too bad at all today. I'll have it looked at next week hopefully. Don't think it's anything to do with airconditioning or temp.

jaffa20

Ok, we still can't seem to figure out how to fix the problem.

Throttle body replaced and it still happens.

Engine temperature sensor replaced and still happens.

With a diagnostic tool, a fault in the ecu appeared so we just sent it off to bba reman in the uk to recondition it. They can't seem to find a problem with it.

I'm going nuts at this stage so i think i might just leave it be and let it annoy me. Would there be something else that i am forgetting about here. Even the mechanic is confused now about what it might be. Anyway. the ecu is still with bb reman and they are going to look at it further. Hopefully they will find the problem.

Eoin

That happened to my Golf a number of times. It didn't rev up on its own too much, but it was prone to losing power from a start. Bit of a pain when you're trying to turn on to a busy road. Throttle body was cleaned, and it was grand (for a while).

crosstownk

I doubt it's an ECU problem. Maybe there is a problem with either your MAF or O2 sensor.

Cleaning the throttle body is one thing but in a lot of cases the throttle angle needs to be reset via a diagnostic tool.