VR6 Sudden Cut Out & Won't Restart

[MikLSP 0]

Hi all, after having quite a long run of trouble free motoring my VR6 decided it didn't want to go to Tatton Park on Sunday where I was ironically going to put it up for sale.

 

Initially it was hesitant on the motorway and then, after stopping for fuel at Preston, the engine started up fine but immediately cut out like turning off a switch.

This occurred maybe ten times and even revving the engine up would not prevent the cut out.

 

Eventually it stayed running but with an extremely erratic idle so I decided to make the short dash to my mum's house nearby to investigate. By then the engine really struggled to pick up revs and continued to idle poorly so I shut it off and disconnected the battery for a while in case the ECU was somehow confused.

From then on it would not start at all; the starter motor turns but there is no attempt to fire.

 

You can hear the fuel pump running and by-passing the relay made no difference so we called the RAC out, then started some strange behaviour.

 

Firstly, the car locked itself (full closure alarm & immobiliser) with the keys in the ignition!

Then, after recovering the keys, the engine started but again struggled to idle with the revs bouncing and occasionally sitting steady at nearly 2,000 rpm.

The OBD report threw up a host of faults, some of which were dubious at best, e.g. cannot communicate with the automatic transmission (well no, it's a manual gearbox) and Hall sensor failure (isn't this to do with the distributer? This engine has a coil pack...).

Also, while the ignition was on and engine not running, some relays were sporadically clicking and the ABS relay would occasionally go berserk for a few seconds at a time.

After a while the engine cut out again, repeated for a few restarts and then returned to not starting at all and refused to communicate through the OBD port.

 

I was left quite demoralised and without an answer other than possibly "significant wiring problems or faulty ECU" so I'm not sure where to go.

 

There's fuel and spark as evident by the odd bout of starting and while things like the ISV, MAF & crank sensor could explain the rough idle, would they prevent the engine from starting all together?

The immobiliser could be a factor, especially considering how the car randomly locked itself, or just a bad earth somewhere?

[fla 9]

sounds like some loose wiring somewhere as the symptoms are quite pronounced. Check the main round connector on the right of the engine bay - see if its clean (no corrosion) and no frayed or broken wiring.

If its cranking then hopefully the ignition switch is ok.

Did you check the ecu relay 109? If not, then bridge the connections if you don't have a spare relay to hand. Maybe also follow the wiring from the crank sensor to see if that's not somehow damaged. Might also be worth removing it and giving it a clean - there may be some swarf on it.

Have you removed the relay panel recently? If so you may have disturbed a connector at the back.

[MikLSP 0]

Yeah, checked the main round connector and that looked good, nice and clean etc.

 

Not tried the ECU relay actually, that's worth a look. Not moved the relay panel but I did have a look around for any loose connections or earth wires etc. after the problem.

 

Would the crank sensor prevent the engine from firing at all or just make it run poorly

[Dox 23]

Faulty crank sensor = no spark at the plugs and no fuel injected either.

 

Check the battery connections and the main battery to body / engine earth connections

[CazzaVR 0]

Also worth cleaning the factory immobiliser plug if you have one and check that the plug to the back of the clocks is secure.

[MikLSP 0]

Having trouble getting hold of a crank sensor (partly because the shop who had one for me to collect today is now strangely closed for a week instead).

 

Anyway, in the meantime I have tried to find some info on testing the sensor and apparently they should give a resistance of 500-700 ohms between two sensor pins and at ECU pins 67 & 68, mine reads ~535 ohms at each so it seems to be OK.

 

Not sure if I have a factory immobiliser, where is it located?

[CazzaVR 0]

Remove driver under tray. Trace black wire from ignition barrel to little black box up near the spoiler switch inside the dash. Remove plug and clean with we'd or contact cleaner. Plug and unplug several times, spraying in between.