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Author Topic: Strange engine issues - occasionally stops, refuses to start when hot  (Read 393 times)

Offline frozenchosen

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Hi all!
New member here, living in Norway.

My 2007 mk5 1.9 4motion started misbehaving today. First, it was a refusal to start when the engine was warm - plenty of cranking power, but would not fire. After allowing the engine cooled for a while, and after several failed attempts, it then started with a bit of coughing and spluttering to start with, then behaved as if nothing had happened. Took it for a test drive for a few minutes and all seemed normal, but then the engine died when I stopped at an intersection. Refused to restart until it had cooled for about 20-30 minutes. Managed to make it home, but was careful to not allow engine to go to idle at intersections. Made it home OK. Tried stopping and restarting the engine, but it would not restart.

No error codes on VCDS.
Cranking was strong and even, at about 300 rpm.
Water temperature sensor showed about 85 C.

Again, after about 30 minutes or more, it started with a bit of coughing. New test drive seemed fine, until I slowed at an intersection and the engine went to idle and died. Refused to restart. Good cranking power, but not a sign of life from the engine. After several attempts if finally restarted after about 35 minutes. I drove home and left the engine idling for a long time without issue, yet when I stopped it, it would not restart again untilit had cooled.

Summary:
- Engine will not start when hot - not just difficult/slow to start, but a refusal to start.
- Warm engine may die while driving if it is allowed to go to idle, yet when parked at a steady idle it does not die.
- No error codes or other symptoms.
.. and I was due to leave town for a few days and leave my wife with this car!  :confused:

Have looked on this forum and a number of others to no avail.
Any suggestions greatly appreciated.  :happy2:
Regards,
a friend in need

Online GreigC

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Re: Strange engine issues - occasionally stops, refuses to start when hot
« Reply #1 on: August 23, 2023, 08:39:21 pm »
Sounds like crank position sensor.

Offline Octoparrot

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Re: Strange engine issues - occasionally stops, refuses to start when hot
« Reply #2 on: August 23, 2023, 08:59:14 pm »
Agree, does sound like a failing crank sensor.

Offline frozenchosen

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Re: Strange engine issues - occasionally stops, refuses to start when hot
« Reply #3 on: August 24, 2023, 02:51:10 am »
Thanks for your suggestions.
Is it possible to test the sensor using vcds or some other method?
Would a faulty sensor normally trigger a fault code? (I have no fault codes.)
And where does vcds read engine RPM if not from crank sensor? (I still get good RPM readings when the engine fails to start.)
I hope you don't mind me asking. I'm just trying to understand this and narrow things down.

BTW - Apologies for asking about a non-GTI vehicle here.