2005 Audi A8 errors P0174 and P0171

[koziolek]

Have another A8 in shop with P0174 and P0171,
did smoke test 3 times already no intake leak,
replace MAF sensor and did not help, after 2 days codes come back
and another strange thing is the engine accelerates up and down by itself
when it reaches around 2500rpm, below that and around 3000 rpm its fine.
have no idea where should I look now .

[teuton]

What does the freeze frame data looks like?.

What are your actual fuel trims at idle,at 1500rpm, at 2500rpm and at 3500rpm??

With VCDS check MWB 32 and 33.
Give some useful data and diagnose this car using your scantool......

[koziolek]

fuel pressure ok according to all data 4 bar at idle and around 3 bar after 10 min engine off




http://www.digital-kaos.co.uk/forums/attachment.php?attachmentid=315070&stc=1http://www.digital-kaos.co.uk/forums/attachment.php?attachmentid=315071&stc=1http://www.digital-kaos.co.uk/forums/attachment.php?attachmentid=315072&stc=1http://www.digital-kaos.co.uk/forums/attachment.php?attachmentid=315073&stc=1

[teuton]

Mate,

the computer is taking fuel away at idle and high idle, around 1500 rpm. then, with raising rpm the pcm is adding more and more fuel. This looks like a skewed MAF reading, although you stated that it was changed. (new OEM sensor?)

Does the freeze frame data show the code set with high engine load and rpm/tps signal? If so it is another indicator for the MAF. While snapping the throttle you should get a reading of at least 100g/s.

Did you check the fuel volume and not only the pressure?

[impactops]

I gather you have checked for leaks


http://wiki.ross-tech.com/wiki/index.php/16555/P0171/000369
http://wiki.ross-tech.com/wiki/index.php/16558/P0174


http://repairpal.com/OBD-II-Code-P0171-and-P0174


Regards
Impactops