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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21622
Experience:  BEng hons Mech engineering, in auto industry 22 years
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a3 3.2 v6 54 plate ,car failing to idle replaced maf sensor

Customer Question

a3 3.2 v6 54 plate ,car failing to idle replaced maf sensor was fine for 24 hours problem returned sensors on maf looked dirty cleaned them problem remains
Submitted: 3 years ago.
Category: Audi
Expert:  Matt replied 3 years ago.

Matt :

Hello

Matt :

I'd next suggest cleaning out the throttle body as they can get coked up

Matt :

if you remove the inlet hose and use a rag with some brake cleaner to wipe it out

Matt :

This could also 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.

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.