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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21707
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a fault on my Audi A6 2.0 tdi S-Line with a multitronic

Customer Question

I have a fault on my Audi A6 2.0 tdi S-Line with a multitronic gearbox where under load my car judders excessively. It is possible to accelerate through the juddering but there is still still an indication similar to a misfire present although not as exagerated.
On initial start up when the vehicle is cool/cold the fault condition is not as evident but as the vehicle warms up and reaches normal working temperature the fault worsens.
Submitted: 3 years ago.
Category: Audi
Expert:  Matt replied 3 years ago.
Hello

as you may have read about already, the multitronic gearbox is not Audi's finest hour

slipping and loss of drive are quite common issues with multitronic boxes as they get past 50 to 60K miles

now a fluid change together dropping the sump pan off and cleaning out the filter screens can often help but often the box has to be rebuilt with new clutch packs to restore full function

sorry this isn't better news
Customer: replied 3 years ago.

I have just had a short engine change carried out with a reconditioned unit, due to a loss of oil pressure, the fault i have referred to has only appeared post re fitting of the engine.


Once the vehicle is warm (at operating temp) the vehicle idles erratically and judders under drive condition under load.
I appreciate there are issues with the multitronic units but there was no juddering or erratic idle present prior to the engine change.

Expert:  Matt replied 3 years ago.
Hello Graham

Ok

thanks for the extra information in which case this could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out causing rough running.
As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

the ECU uses the airlfow meter signal to control gearshift quality as well as controlling the fuelling so a faulty signal can give you the issues you describe

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.
Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.
Customer: replied 3 years ago.

Matt,


 


Thanks for that tip. I passed it onto the garage that fitted the engine and they carried out the checks (something they have carried out previously) utilising acetylene, which apparently achieves the same results, but could'nt find anything.


 


Any other thoughts ?


 


Graham

Expert:  Matt replied 3 years ago.
Hello Graham

OK in that case its possible one of the sensors on the new engine may be giving issues

I'd 1st suggest checking the connection plug and wiring to the following;
Airflow meter
Crank position sensor
Cam position sensor
O2 sensor
Throttle position sensor

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.
Customer: replied 3 years ago.

Hi Matt,


 


Apologies i have not replied or rated your feedback as yet. I am currently in the process of feeding your suggestions back to the garage to implement and hopefully rectify the issue.


 


I could provide feedback now as Ok or even Good but if the guys at the garage carry out some of your suggestions and rectify the issue then it would be an excellent.


 


So would you like meto feed back based on your suggestions, which all sound credible by the way, or await the out come and hopefully resolution to the issue in which case it could be an excellent. Thanks for your help so far.


 


Regards


 


Graham N.

Expert:  Matt replied 3 years ago.
Hello Graham

thats fine

only rate once you're satisfied

if you need any further help then get back to me on this post

there's no need to raise another question