I have a petrol-driven manual Audi A4 1.8 Avant, and it all works well
except that it won't start if I have driven for twenty mintues in the
previous half hour.
If I pull out an end of this tube:
which my French mechanic calls a brake servo decompression tube - and
wait for ten minutes it starts, but then it stalls when it should idle
unless I put it back. Once the engine is running everything is fine.
Otherwise if I wait half an hour for it to cool down it starts again.
I replaced this tube a month ago - the old one had started to pinch,
so I got the exact same part from Audi. Unfortunately that did not
solve the problem.
Can anybody help?
Thanks a lot,
I can't really see clearly from the pics, but do I take it you
are a Brit living in France?? (If so, nice).
Anyway, the French-to-English translation for "servo
decompression tube" would obviously be the vacuum hose, which
supplies the brake servo. Somewhere along the length of this
hose, between the inlet manifold and the servo will be a
non-return valve. See if you can check this.
However, the non-starting and poor warm idling would suggest
something else. Firstly, does any of the warning lights in the
dash light up? Have you got the ECU scanned with a fault code
Regarding pulling off the tube and waiting for 10mins - I think
this is just coincidental. Try to wait those 10mins, but without
pulling off the tube, and see if it still starts. Regarding
stalling with the tube off, that is simply down to the incorrect
idle vacuum, and would be normal.
Your actual problem indicates fuel vapour lock when hot. Do you
smell any fuel vapour when the bonnet is open. Are you able to
examine the fuel lines? Have any of the underfloor rigid lines
been partially crushed from hitting a rock or similar. Are any
of the flexible fuel lines (particularly under the bonnet)
degrading, and do they feel limp and sludgy when warm. The
internal bore of the fuel hose can collapse, but not be evident
on the outside.
Another issue could be the fuel pump. These are ECU controlled,
to give variable pressure and delivery rates. It is not unheard
of for these to fail.
Hope these are some pointers to get you started, rgds.
www.VAGSport.co.uk - forum dedicated to all makes & models within
Coolant Temperature Sensor might be faulty. It might be richening up the
mixture enough to flood the engine and you have been starting the engine
with an additional amount of air.
Spark plugs might be worn too.
Thanks Sean and Dave - this is really helpful information. I will get
the Swiss mechanics on the right track now.
As for Gerky, cheers mate - maybe they'll swap it for a TT quattro if
I throw in the furry steering wheel cover!
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