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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21716
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have 2007 audi tt tfsi 2.0 Thrown the code P0171. Cleaned

Customer Question

Hi
I have 2007 audi tt tfsi 2.0
Thrown the code P0171. Cleaned the MAF sensor and checked hoses, which appear on good condition and no apparent whistling noise / obvious vacuum leaks.
Reset the code but has now come back.
Drives Ok but at idle when engine is upto temperature the revs rise and fall in a cyclic fashion from 800 to 1300 revs. Also when coming to a stop with the clutch in the revs sometimes "hang" at 2000 before dropping to idle.
Could this point towards PCV failure or are there other thing I should be checking?
Many thanks
Submitted: 1 year ago.
Category: Audi
Expert:  Shantal-Mod replied 1 year ago.
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Expert:  Matt replied 1 year ago.
Hello
1st check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate. this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers also check the condition of the clutch position switch on the pedal as this is responsible for changing the idle speed control when shifting gear
Expert:  Matt replied 1 year ago.
Hi
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