Help Advice Needed Please.

[bilko0795]

I am still having a niggle in the car with the revs dying away to nearly stalling it mainly happens when the car is cold but is now starting to do it all the time, It's when i slow down for a junction or roundabout and dip the clutch to change gear, as soon as I dip the clutch the revs drop rapidly and then fly up to 1200/1500 rpm then drop back to the normal 800 rpm and idles quite normal as soon as a gear is selected and the clutch released, until I pull of again and it starts all over again I have been my head now trying to figure this out and I am at a loss. I have just come of the phone with Tps ref prices for the parts I think might be the culprit and to be honest £685 .20 is a bit steep.

So has anyone got any ideas as what could cause these symptoms.

My thoughts are Isv, Throttle idle switch or Air temp switch. I can't find a Isv to try and eliminate that piece of the puzzle and the other two items are stealer parts only and I don't really want to buy all three if no need.

Oh yeah I have also noticed that if I coast down the hill to the junction with the car not in gear and change into gear when approaching the junction it doesn't lose the revs

ANY IDEA'S PLEASE BEFORE AUDI ROB ME OF NEARLY £700

[sidrick]

Have you pulled the codes? How's the car running? Have you checked the ISV is free moving and the fuse is okay?

[SteveH]

I have the same issue on mine but it's intermittent. Probably an old, worn ISV. Vagcom will allow you check codes and watch the temp senders in real time. There may not be any codes stored for this issue as it could be the ISV sticking. The throttle idle switch is easy to test with a multimeter.

[Rusty]

Have you checked the idle switch?

Disconnect the breather system to eliminate it. Remove the connection under inlet manifold and block it at both parts with an M8 bolt and clip.

[UrS4boy]

ANY IDEA'S PLEASE BEFORE AUDI ROB ME OF NEARLY £700

What is the state of your throttle closing dashpot? The dashpot is there to slowly close the throttle plate when you take your foot off the gas. This gives the ECU some time to adjust to the change and also start to bring the ISV into service. It sounds to me that your dashpot is either broken or not properly adjusted and when you are taking your foot off the gas pedal, the throttle plate is slamming shut. Under these conditions, the ECU seems to panic and opens up the ISV too far (hence the 1200 RPM) before it realizes the situation and controls the ISV normally.

Here is an AAN dashpot. The 3B, ABY and ADU dashpots will be similar and located on the throttle body.

[AUDIDAVES4]

I've just sorted the same issue on my avant by removing
& cleaning the throttle body running perfect now .

[bilko0795]

Sidrick, No codes showing on vcd's fuse ok and car running fine today on way to work but back to issues on the way home tonight.

SteveH, I will bite the bullet and buy a new Isv and learn how to use vcd's

Andy, will check that on w/end.

Dave, the Dashpot has been disconnected for the last four weeks as I thought it was the problem and took it off to confirm I will refit it and check again. It does look as if it's ok as the paint marker on the thread as not been broken.

AudiDaveS4, I will clean the throttle body and hope it does the trick as I have already cleaned the Isv.

Thanks for all the input.

[newsh]

Also clean the MAF connector

[UrS4boy]

... Dave, the Dashpot has been disconnected for the last four weeks as I thought it was the problem and took it off to confirm I will refit it and check again. It does look as if it's ok as the paint marker on the thread as not been broken..

It might have been the problem but taking it off would not solve the problem. Recommend replacing it with a know good dash pot.

PN is 034133283 and it seems to common to manual transmission Audis from 1987 to 1997.

[johne]

My late ABY never had a dashpot fitted from the factory and it's managed 165,000 miles fine without it.

John

[prj]

Usually such stalling is due to boost/vacuum leaks.
This accounts for 99% of cases.

The other 1% tend to be the ISV.

[bilko0795]

Newsh, maf connector clean also brand new maf fitted.

Dave, as said I will refit on w/end

John, Same as you when I purchased the car it didn't have a dashpot fitted I found it resting on the front subframe three months later, had no issues from Aberdeen to South Wales.

Dimitri, Has been boost leak tested after fitting a full set of Rhoose hoses no leaks found but I think you could be right as I have now fitted two Homefry ecu's now and both are performing as a standard one only boosting to 0.7/0.8 I have a sneaky feeling it could be one of the smaller hoses that could be to blame just got to test again and find.

[prj]

So you already found your problem - if it is only boosting 0.7-0.8 bar you clearly have a big boost leak. And that is why it stalls.
Only other thing could be the TPS not giving full signal, but it would be too much of a coincidence IMO.

[bilko0795]

The reason I didn't give it much thought towards a leak as the two ecu's I have were boosting to 1.2 bar but had a lot of violent jerking along with it, tested the car for leaks found a leak on the intercooler done the h mod all was fine as said boosting to 1.2bar with no jerking, as said now boosting to 0.7/0.8 but no jerking just smooth acceleration So my thoughts were not directed to a leak. I was also advised on here that it could be maf related so went and bought a new oem one from Audi but the niggle is still present but this morning no problem at all. So tomorrow I will spend a couple of hours leak testing.

[sidrick]

Just in case you end up requiring an ISV, I bought mine from here - http://www.ebay.co.uk/itm/IAC-Idle-A...-/131041685912 and it's been spot on Cheaper than Audi, I'm sure....