Help ! Intermittent bad running now won't crank !

[dynochap]

Hi all, this is my first post and I'm hoping someone may be able to help.

A week ago I nipped out to the shops, and my engine started to run bady - "kangerooing" with the slightest throttle application. I stopped, switched off, and on restarting the problem was gone. It was a hot, sticky day. After reading a lot of the threads here, I suspected I was looking at a MAF or oxygen sensor issue.

Then, 3 days ago, about 5 minutes into a journey, the engine died completely. I coasted to the side of the road, stopped, and on restarting, everything was fine. I pulled away, only 2 minutes later the engine died again. This time the engine wouldnt even crank ! I checked all the fuses, found nothing, so got back in the car and tried again. It started and ran perfectly. Again, it was a hot sticky day.

Then, yesterday afternoon (another hot sticky day) - I went to the car to leave work, and it wouldnt crank. After repeated trying, it suddenly cranked and started, and ran fine for a few minutes, after which it cut out for about a minute. I restarted, and it ran fine.
Can anyone offer any advice ?
Can the ECU over-ride the cranking signal, or can only an aftermarket immobiliser do this ?
When the problem occurs, i.e no cranking, all the other electrics seem OK.

[kingos2]

maybe

sounds a bit like the hall sendor's on its way out if it's an aby someone will correct me if im wrong,best thing to do is get it vag-com at a friendly garage with the motor running,someone had the same problm on here a few months ago.think cheap!then work up,if wont start try poring hot water down the cam gear when turning over i'll get you to the garage

[dynochap]

Would the hall sensor actually stop you cranking though ?

[kingos2]

yes as far as i know if you unplug the hall sensor behind the cam gear the car wont crank, it could if the sensor behind the cam gear is kaputt the ecu cant tell the hall sendor at the flywheel the speeds of each other or vicy versa puting it out of sync take a look at other threads type hall sensor into search that will help explain better.

[martinjs]

Check to see if there are any fault codes stored.

[~Delta]

Just tried unplugging an ABY crank and cam sensor, it still cranks over, just no spark.

[dynochap]

Thanks Delta - that rules out cam and crank sensor then.......

[dynochap]

Just an update - the car has worked perfectly for two days now - wondering if heat / humidity could play a part. Anyone know if this is typical of poor earthing issues / corrosion on terminals ? Also, might look for corrosion under the fuse/relay try - does anyone know if there is a seal that might be damaged underneath it ?

[dynochap]

OK, I've just checked the blink codes, and the only one coming up is 2224. This has come up at the dealers before, so I think it is only a minor air leak. I dont believe that this can be responsible for the engine shutting down completely and refusing to even crank can it ?

Does anyone know:- If you lose the 12v feed to the ECU (but not the starter), does this activate the immobiliser and prevent cranking ?

[Doug_RS2]

So the car does not even turn the starter motor?

Have you checked the condition of the heavy duty wires to the starter?

Do you get a clicking when you try and start?

[dynochap]

Hi Doug - no, no click, ie there's no response from the solenoid or starter, hence wondering about immobilisation. Unfortuneately its an intermittent problem - at the moment it works fine.
Its got two immobilisers - the factory "chip in the ignition key" one, and an aftermarket Codealarm.

[Doug_RS2]

I would find where the aftermarket immo connections have been spliced/cut into the loom and check that they are ok.

It is common for these connections/splices/cuts to cause problems with aftermarket immobilisers.

[4WheelDrifter]

I have to wiggle my alarm/immobiliser loom every now and again.
It's a shame you can't get Thatcham approval for fitting them properly.