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Audi A4 1.9TDi PD AWX 2002 - Intermittant mis-fire under light load, code 17994 P1586 #

Posted by Paul Foster on December 15, 2009, 3:48 pm

Year of Manufacture *: 2002
Engine Code or CC *: AWX 1.9
( Optional ) Scanner Used: Solus-pro

Hi All,

Got his one with a slight hesitation/mis-fire when it's still cold. It also sometimes sounds a bit lumpy on idle when it's cold.

Fault code 17994 or p1586. Solus says engine mounting short to earth! I guess there's more to it than that!

The problem's so intermittant that it's difficult to see it faulty.

I checked the switching time on the cylinders on live data - cylinder two was showing about 26 (ms?) while all three others were around -17. However, when I saw this it was running ok.

Does this ring any bells with anyone?

All silver bullets gratefully recieved!

Cheers - Paul.

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by John Ritchie <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT2638' width='330' height='300' border=0 style='border:none;'> on December 15, 2009, 8:15 pm, in reply to "Audi A4 1.9tdi PD Intermittant mis-fire under light load"
John Ritchie

Got this from a vw forum
Looks like engine mounts

"the way the mounts work is that there is a fluid chamber with a plastic body in the middle of it, with small channel cut through it. this allows fluid from the top chamber, through the plastic body, to the bottom chamber. the bottom chamber is rubber lined and can deform under pressure. there is also an airway vented to atmosphere, with a rubber membrane separating the fluid from the atmosphere. a solenoid valve, controlled by the motronic, can open or close the airway.

below 1100 rpm (i.e idle), the engine vibrations are not enough to force fluid from the top chamber, through the passageway to the bottom chamber. the airway is open (solenoid valve open). the rubber membrane creates a soft cushion which absorbs the high frequency vibrations.

above 1100 rpm the solenoid valve is closed which blocks the airway and so "hardens" the mount (the fluid has nowhere to go). thus the mount is effectively solid.

the high frequency vibrations at speed are absorbed by the membrane (as in the idle case), while the more damaging low frequency vibrations cause the fluid to force itself through the chamber in the plastic body to the lower chamber, forcing the (lower) rubber chamber to distort - effectively absorbing the vibrations.

in this case i would suspect that the mounts are bad - possibly as simple as the connectors have been pulled off"

HTH
John

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Paul Foster <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT2680' width='330' height='300' border=0 style='border:none;'> on December 15, 2009, 11:16 pm, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"
Paul Foster

Wow! I never knew that!

Got to be worth a look.

Thanks very much for that.

Paul.

Ne te confundant illegitimi

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Peter Macdonald <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1631' width='330' height='300' border=0 style='border:none;'> on December 15, 2009, 11:44 pm, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"
Peter Macdonald

Hi Paul, We've had one of these codes for an engine mount on an A4 for a year or so with no other obvious problems.
I'd suspect something else rather than the engine mount. More details tomorrow when I'm back in the workshop.
Peter

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Peter Macdonald <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1631' width='330' height='300' border=0 style='border:none;'> on December 16, 2009, 7:43 pm, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"

Hi Paul,
Same car - A4 Avant AWX 2002 - October last year.
Yes, same code for left engine mount. The owner didn't want it replaced ( I think it was around £150 ) and has never reported any vibration or other problems. We've serviced it several times since and the code is still there but no other problems.
Peter

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Dave Mc Gee <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1044' width='330' height='300' border=0 style='border:none;'> on December 16, 2009, 8:05 pm, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"

Hi all,
I had this last year also,my fault cleared after replacing the DMF,the vibrations in the DMF were causing the engine mounting to flag a fault code.
HTH
Dave.

Cheers,
Dave.

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Peter Macdonald <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1631' width='330' height='300' border=0 style='border:none;'> on December 16, 2009, 9:58 pm, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"
Peter Macdonald

Hi Dave,
Did you investigate & replace the DMF to cure the engine mount problem or a misfire or was the DMF just clearly knackered from the start?

Peter.

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Dave Mc Gee <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1044' width='330' height='300' border=0 style='border:none;'> on December 16, 2009, 10:19 pm, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"

Hi Peter,
I had the same symptoms as you have,i got advice which led me to replacing the flywheel,like you...i found it hard to see how the engine mounting would cause the fault.I investigated misfires which led me to a dead end and then i replaced the dmf(reluctantly due to the cost),my engine mounting code then cleared and never returned,maybe your customer could let the problem progress until it gets to a point where the it might be more obvious.
I hope i am not leading you down the wrong path.

Cheers,
Dave.

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Peter Macdonald <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1631' width='330' height='300' border=0 style='border:none;'> on December 17, 2009, 8:58 am, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"
Peter Macdonald

Thanks Dave,
I hadn't noticed any misfire but I will look at it more closely next time it's in. Perhaps the DMF is Paul's answer.....
Regards,
Peter

Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load

Posted by Adam Sutton <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1942' width='330' height='300' border=0 style='border:none;'> on January 8, 2010, 12:44 pm, in reply to "Re: Audi A4 1.9tdi PD Intermittant mis-fire under light load"
Adam Sutton

I've seen this before, I'm not saying this will always be the cure but it's worth investigating. It turned out on the A4 8E Avant we had in that the one way clutch in the alternator pulley was seized up. This caused the alternator belt to jump & vibrate.This was causing the whole engine to vibrate at tickover (honestly). We changed the pulley which smoothed out the vibrations & no more problems. Hope this helps.

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