VW 1.9 TDI intermittent cough

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Mon 16 May 2005 23:01
VW 1.9 TDI intermittent cough - Sofa Spud
I posted about this problem on our 94 Passat 1.9 TDI estate before, ages ago, (www.honestjohn.co.uk/forum/post/index.htm?t=24091 ) but the problem persists and is a mystery.

The symptom is an occasional cough, or misfire that occurs randomly - on tickover, when accelerating or cruising at constant speed. Some days it doesn't happen at all, others a lot. Other than the misfires the engine runs normally - turbo works OK and no smoke from exhaust. The car has done 153,000 miles.

The garage has ruled out a fuel pipe/pump problem.

Possible causes that occur to me are:
Faulty connectors in engine management system.
Faulty 'Relay 109'
Sticking EGR valve
Engine stop solenoid cutting in momentarily.

When the key is in the 'run' position, but without starting the engine there is an alternating rapid ticking from the wastegate actuator solenoid on the bulkhead and then a quicker 'buzz' from one of the electronic bits on the injector pump.

Occasionally the engine will cut to default mode while running, when there is no noticeable boost from the turbo.

Any TDI experts out there who can throw any light on this longstanding problem? It's getting worse now - I could live with the occasional jolt while driving but now it's getting worse.

Cheers, Sofa Spud (alias 'the Passat misfire bore')



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Tue 17 May 2005 12:21
VW 1.9 TDI intermittent cough - Sprice
A lot of backroomers swear by Millers diesel treatment, perhaps your car needs nothing more than a bit of Millers (or STP, Wynnes etc) and an Italian tune up?!
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Tue 17 May 2005 20:26
VW 1.9 TDI intermittent cough - Sofa Spud
Thanks. I tried Redex Diesel treatment and also an injector cleaner additive, but no change. I feel there can't be anything wrong with the basic mechanicals of the engine as it runs so well when it's not misfiring. It must be do with engine control systems.

Cheers, SS
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Wed 18 May 2005 14:09
VW 1.9 TDI intermittent cough - stokie
I suffered from something similar after I got a garage to change the fuel filter on my 106 non-turbo diesel. It did diminish over time, next time I changed the filter I followed the instructions on bleeding air out - basically squeeze the bulb device a few times.

Other thoughts are an air lock in the fuel, does the fuel cap let out a loud sigh when removed?
Try Shell Diesel Extra fuel, my pug ran smoothest on that.
Check any breather pipes you can find for splits.
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