Rough Idle

[melman]

Over the last couple of days my 1.8T has started to idle strangely! After going up in the rev range and then taking my foot of the throttle (clutch down or out off gear) the revs drop to 1400 for about 5-10 seconds. They then bounce down to 850 and then fluctuate between 750 and 1000. Not sure if this is connected but I had a quick look under the bonnet yesterday morning (from cold) and noticed both the fans were running? Checked the thermoswich (in pipework just behind rad) and it was closed circuit, I would have thought this would be open circuit when cold. I have ordered a new one to see if it cures the problem. I also cleaned the MAF sensor just in case but it was spotless!

Any ideas people? /ubbthreads/images/graemlins/confused.gif

 

[audi_girl]

Coil Pack?

My answer to everything at the moment, can you tell I am slightly sensitive about it !!!!

But seriously - my first symptom was uneven idling...

 

[melman]

It has crossed my mind. /ubbthreads/images/graemlins/frown.gif

How much did that set you back Audi Girl?

 

[audi_girl]

It'll be free as it's faulty components (Audi are releasing a design modification - their 3rd incarnation of the coil pack apparantly!)

It's more a matter of "when". When mine went I got told to expect the car to be returned in mid-March. Every dealer has loads of cars waiting for 1-2 coil packs /ubbthreads/images/graemlins/confused.gif

Nothing you can really do if that is what it is. You will know if it is - warning light on the dash, and the car will feel virtually undriveable - very lumpy.

 

[melman]

Cheers for the info Audi Girl. As yet there is no warning light and the car seems to be driving as normal. I am going to pick up the new thermoswitch soon so I will see what happens after fitting!

 

[audi_girl]

Good luck! Pray it isnt a coilpack though. If you come to one of the meets someone could plug VAG-COM in.....

 

[audi_girl]

Ahhhh that remind me - the Dealer forum is missing. I'll create it tonite - then post you recommendation / or NONrecommendation of a dealer there !

 

[melman]

Just picked car up from dealer without having repair carried out and they didnt charge me for diagnosis!

That was a pleasent surprise! /ubbthreads/images/graemlins/beerchug.gif

 

[melman]

Not sorted yet but do have some more info....

Took the throttle actuator off the car on saturday and stripped it down. Not much in there really, just a motor and a fancy potentiometer. Gave it a clean (although it looked spotless) incase it was sending a false reading and then put it back on the car but the problem is still present.

Going to book it in at another dealer for a second opinion seeing as the first didnt cost me. /ubbthreads/images/graemlins/smile.gif


Dave, do both your rad fans come on as soon as you start the car from cold? Not sure if this is connected to the problem or not? I just think maybe the throttle actuator is being told to behave like this as the cars not sure if its hot or cold?

Look forward to your reply,
Melman

 

[[Dave B]]

I'm not sure if the Rad fans come on direct from cold, i'll check tomorrow morning and then post. They may do as the car takes ****** ages to get warm.

 

[Moresauce]

My A3 did this a couple of times on startup in the mornings but thankfully nothing since that about 4 weeks ago! Fingers crossed.

 

[Loretta]

I got this problem with my car. Irratic idle between 700-1000rpm. Can happen at any time. Can drop so low that it stalls... Pain in the bum. Hopefully just due to power steering pressure sensor. Poxy cars these days have so many sensors that any one that fails often causes a problem like this. VAG 1551 normally picks up anything dodgy. Make sure you get a complete print out when you take it in for diagnostic checks though! Good luck!

 

[gaz238]

i`m no expert but after reading these forums the coolant temperature sensor (not the thermostat) seems to create this kind of problem - mine`s on order

 

[rodenal]

Lol, u resurrected a 4 year old thread for that?

 

[WKDLAD]

Hmmmm my car seems to do this to. and i have noticed that as soon as i start my car up, the fans are on. Do you think this could be my coolant temperature sensor ? if so were is it?

 

[gaz238]

sorry, didn`t realise it was an old thread

 

[WKDLAD]

hey gaz how much is your sensor and also were is it located?
Thanks

 

[gaz238]

£20 inc vat and delivery from vagparts.com. audi wanted over £30. on the a6 it is located at the back below the air ducts/air mass sensor. mine was green and this is how i identified it, but the older ones are blue/black which are prone to fail

 

[mikeoh]

Some of you might find this interesting...

I've had idle problems, but it's between 1000 and 1400rpm waves about a bit settles on 1200 then slowly down to 1000. Temp gauge on dash was reading a solid 90 under most if not all driving conditions. However having read about these been prone to failure i ordered a new one and replaced it.

I got mine from SAS autoparts who are local to me and it was around £18. I was a bit concerned that the sensor i was replacing was the newer green coloured one. Anyhow after I changed the sensor i still have the idling problem. But my temp gauge on the dash only ever gets to 90 when i'm sat idling in traffic for several minutes and in normal driving it sits on 70 or just below. This leads me to think that the original sensor might've been knackered AND that my thermostat is knackered. Also i just drove the car 20 yards off the road onto the drive and the pipe from the engine to top of the radiator was slightly warm which i'm sure it shouldn't be after the engines been ticking over for 30seconds. I'm going to have a go at changeing the thermostat this weekend i think and hopefuly (dear god please!!) that will fix my idling issues.

I'd be interested to hear if anyone else has had any thermostat related idling problems.