Idle question

[pmj]

Hi all. Just bought a sprint blue 2010 s4. Whilst on the test drive I noticed that when in traffic if I lifted the clutch when out of gear the revs on the car would rise. But it didn't do it all the time only some times Is this a feature of the car like an anti stall thing ?

[Silverfox42]

Were you moving?
If so, normal.

If not, strange

[pmj]

No. Car was stationary not in gear. Handbrake not on. But when releasing the clutch the revs rose to about 1000 rpm then back to normal idle. It also did it when pulling away. ?

[Silverfox42]

Sounds like it is trying to recover from a stall that never happened.
Do you have VCDS to see if there are any error codes coming up.

My car lifts it Revs to about 1100 rpm if I coast in neutral in slow moving traffic then settles to idle when I stop.

Might be something the supercharged S4's . If the car is within its 3 year Audi warranty, perhaps a visit to your local friendly dealer might either show up a fault on diags or reassure you.

[pmj]

The Audi warranty ran out last month. I have not got the car yet it's still at the non Audi dealers. But if this is not a feature I guess a call to them to get them to investigate and cure if its a problem before I get the car. I did mention it on the test drive to the salesman. But he made no comment.

[adsgreen]

Idle is a funny thing and subject to many factors.

For example, air con pump is fecking huge and can sap a lot of power.
Also the alternator is big enough to have idle issues... then you have the secondary air injection system and other emissions based things that can change things.

Try to take as many things out of the equation as possible - turn off all the ac, reduce leccy loads to minimal (no lights, wipers, heaters etc) and if possibly give the battery a good overnight charge.
See what happens when the car is warm after a longish motorway drive (to give the alternator chance to fill up the battery after starting) - 20-30 minutes should do it nicely.

Then see what happens.

The gearbox input shaft shouldn't be big enough to cause any impact to the engine idle. You should be able to press the clutch any way you want without it missing a dime.

Hmm - I wonder if the S4 has the same clutch switch issue on the b7 rs4... is the car juddery to drive?

[pmj]

I see what. Your saying But on the drive everything was off. Even the radio . It didn't do it everytime I lifted the clutch but more time than it didn't The car drove smoothly and this was the only thing I picked up/ noticed on the drive. Called the garage and told them to look at it and report back before I collect the car.

What was the issue with B7 switch ?

[adsgreen]

I see what. Your saying But on the drive everything was off. Even the radio . It didn't do it everytime I lifted the clutch but more time than it didn't The car drove smoothly and this was the only thing I picked up/ noticed on the drive. Called the garage and told them to look at it and report back before I collect the car.

What was the issue with B7 switch ?

The switch for the clutch position (on/off) can fail and when it does the car assumes some (<beep>) defaults that make the idle a bit wayward and the car a bit jumpy when pulling away and changing gear.

On the drive - was that before or after coming back?

[pmj]

It might have been jumpy not sure as it was a test drive on a manual car I had not driven before so at the time I may have just thought that was the reason and not put the two together...

Can say it was exceptionally jumpy / juddering , it was reasonably smooth...

I have asked the garage to look at it and let me know... if it persists then the garage will see a lot of me until I know its sorted...

But isn't it stupid of me to even think this variable idle might be a standard feature... called Audi to see and I could almost hear the mechanic chuckle ...

[R1NGA]

Hi all. Just bought a sprint blue 2010 s4. Whilst on the test drive I noticed that when in traffic if I lifted the clutch when out of gear the revs on the car would rise. But it didn't do it all the time only some times Is this a feature of the car like an anti stall thing ?

Mine does the same - always has. Trait of a FBW throttle I think and I am certainly not worrying about it.

[adsgreen]

The idle is variable due to the different demands on the car.
For example as mentioned above if you are coasting with the clutch out you may notice a much higher than normal idle and as I understand it this is for emissions purposes.

[pmj]

But should this do this when the car is stationary, with no load on the engine, just raising raising the clutch pedal... I understand if the car is under load...

[pmj]

The answe is no. It shouldn't do that. Had the car 24 hours now and after getting the garage to look at it and do some resets it now has not done in I'm the last 24 hours.