engine surge ??

[nicegollum]

I have a 97 audi cabrio with the V6 2.6 - it has been stored for a few months and when I started it up it ran great until it warmed up - the the revs were going high and low all the time as if I was revving it - can anyone help please ?

[scotty33]

There could be a vacuum leak, but I would expect that to affect the running when cold as well? Or there could be a lambda sensor problem which would only affect the warmed up engine, but usually causes poor fuel consumption too.
You could check that the throttle is returning to it's stop fully when you release the accelerator. Other than that I would suggest you read the ECU for fault codes.

[nicegollum]

Thanks for your suggestions scotty - I'm going away this w/end but next week I'll look into it and tell you how it goes m8 - all the best !

Scott
http://img.photobucket.com/albums/v673/scottmaule/golcar.jpg[/IMG]

[tech1]

hi mate,when you said the car had stood a while, did you have to boost start the battery?how long did the engine run b4 you noticed the rough idle?how long have you let the engine run for with the fault?..In some cases some ECU's re-map if the battery goes flat.and can take upto 1hour idle time to re-configure..

[nicegollum]

Hi Tech1 - thanks for your response - yes I had to put the battery on charge first. The car had been sat in the garage for about 6 weeks, after charging the battery it started up and ran at fast idle ( choke on ) for about 2 minutes I guess, before it warmed up, then the revs dropped to normal tickover. Pretty soon after that it started to go up to approx 2000 revs then drop down to 1000 in a very regular pattern, peaking at about 2-3 second intervals. I only let it run for a couple of minutes as I did'nt know if it would cause damage. I have'nt heard about the ecu re-mapping like that before - do you recommend I start it up and let it run till it returns to normal then ?

Thanks so much for taking the time to help

Scott

[tech1]

hi scott,have you had any result yet?if idle still up and down,let the engine run minimum 30mins,just keep eye on temp,idle is ok as long an does not go above 1/2 its max rev on counter.
It could be also idle speed control valve slightly choked up,trying to balance.may need clean up..hope this helps.

[nicegollum]

Hey there :beerchug: sorry I haven't been back to you - My shifts are a pain.

I ran the car like you said on Tuesday and it actually only did it for a minute before it cleared and ticked over beautifully - I left it running for half an hour in all and it was great - what a relief.
The car only has 68k on it and is in such nice original condition, I was gutted at the thought of any major engine bother.

It's nice to know there are people like you out there who will help when garages will pull you in and take hundreds from you for nothing - thank-you very much ! :You_Rock_

[tech1]

no probs mate,glad i could help...