Rough idle

[Marxy655]

Hi guys new here just signed up I have seen some good stuff on here and I need some help from the gurus

I have a 2008 a4 b8 3.0 tdi quattro and the turbo actuator is playing up.

No loss of power still opens and closes from drive to neutral and reverse to neutral (I have the stronic box) no warning lights on the dash nothing drives lovely and smooth and nothing is at fault until I come to a stop at a set of lights or when I stop to engage reverse. It's almost as if its hunting to find the idle rev of about 800rpm. But at a set of lights sitting in drive it's lurching all over the place and it does it in park too. 1200 rpm down to about 400 then back up and down again and I can see the actuator under the bonnet moving back and forth. Then after a while it settles and stops and just ticks over nicely. It's an intermittent fault but it happens every day but if my missus drives for 2 hours a day it will do it for about 15 mins. Audi want 2400 for a new turbo but I explained the turbo is fine doesn't lose power or smoke or anything...... Any ideas guys I'm stumped.. Thanks in advance

 

[spartacus68]

First off get the car scanned with VCDS to see if there's any error codes logged. What's the mileage? Could be swirl flaps on air intakes. They're electronically controlled but the actuator arm or linkage can wear. etc.

 

[Marxy655]

First off get the car scanned with VCDS to see if there's any error codes logged. What's the mileage? Could be swirl flaps on air intakes. They're electronically controlled but the actuator arm or linkage can wear. etc.

Milage is 136000 at the moment. If the swirl flaps were sticking why would the actuator be opening and closing? Would it be to keep the air flow going to the engine? I'm not clued up on engines much lol
Many thanks for the response

 

[spartacus68]

You need to get the car scanned, otherwise we're just guessing. If the swirl flaps were failing, then the car would have throw a code, probably go into limp mode, etc. Could be as simple as a dislodged vacuum pipe, etc. Check out the section of users with VCDS who are close to you that may be able to help.

You can buy VCDS for about £300 if you have a suitable laptop. If you are new to VAG brand or long term owner then VCDS for it pays for itself quite quickly, considering main dealer will charge you £120 each time they plug in diagnostics which is daylight robbery.

 

[pelhamsdetailing]

As spartacus says, unless you have a scanner to see what the fault code is, we couldn't tell you what it could be. No matter what state the swirl flaps are in, these wont cause the severe rev hunting issues you're having, and as spartacus says, there would be a predominant limp mode.

In the past I have read that a faulty actuator flap located in the top intake just after the MAP sensor caused RPM hunting. It had enough play in it due to wear and tear that it would rattle, i.e. rotate on it's axis, back and forth as the engine ran, which would vary the amount of air going into the engine, which caused RPM hunting.

It's an easy job to check: jubilee clip to take the intake hose off out the way, and then you'll see an intake flap in the open position by default. This closes briefly when the engine is shut off to starve the engine of air and cause a clean engine shut-off. Give it a push, and if it's not springing back to it's default position or is very, very loose or super easy to move, then that is potentially your issue. It costs you nothing to check, only 5 minutes of your time.

All the best

 

[Marxy655]

Well guys, had car scanned and it had a few faults with the dpf and a few sensors picking up too much ash and soot due to a clogged dpf, so dpf has gone egr has gone and now its a stage 1 very happy with the results and just going to see if i can replace the back boxes with some straight pipes for a slightly better puurr from the v6 but i cant thank you guys enouvj for the replys and trying to help out so thankyou and its much appreciated