Cutting Out

[henrym3]

X drives perfect then just cuts out, doesn’t matter what speed, idling along in traffic or 50mph. Will restart and run perfect again. Has happened about 4 times. Diagnostics does not show any faults. I have sent for a new ignition switch, Does this sound like a good idea or has anyone got a better one.
This is an edit :- passed the MOT yesterday without any issues.

[X5Sport]

IGN switch/wiring. Dodgy wiring around the injectors? As in a loose connector/cruddy pin? Loose earth? The only way to stop a diesel is cut the fuel/supply, so something causing that to drop on the electrical side.

I hate modern cars as the computer just shrugs it’s shoulders and takes the ‘nothing to do with me’ line

Good news about the MOT.

[Leslie]

Do a smooth running test on the injectors , mine showed injector 5 but injector 6 was also faulty but didn't show up as a code . It cutout as I was driving along too.

[henrym3]

Thanks for both reply’s. I’ll look into the both as it is very disconcerting when you haven’t got any power steering or decent brakes. I think as an added precaution I’ll bung on a new engine to chassis earth lead.

[marti]

Have you checked for water ingress on injectors 5 & 6, this happened to me and it was the plastic scuttle panel which had a crack in allowing water to drop on the wire to 5 & 6.

[Greydog]

If I recall Henry is driving a V8 4.6is, injector failure 5 and 6 tends to be common on the 3.0 Diesels, though why BMW programming cuts the engine instead of causing a misfire is a mystery.
I would be more inclined to look towards the ECU pins for corrosion or poor contact

[Leslie]

if its a petrol id be more inclined to think crank sensor for random cutout but it could be a lot of things

[henrym3]

Just an update smooth running is really good all cylinders. ECU pins are as new. Can’t see any issues with injector wiring. Removed the earth lead which is in good nick but cleaned all contact surfaces anyway. As for the crank sensor it’s not very old (2 years) and is genuine BMW, when it went south it showed on diagnostics. I was changing the ignition switch today when friends turned up so had to abandon till tomorrow.

[henrym3]

So finished the ignition switch and while in the garage I fitted a new set of heater valves and auxiliary water pump to try and resolve the heater only blowing hot air through the passenger side, needed to run for 1/2 mile at 4K revs to get heat in both sides. It has been bled so often without resolving the issue. Diagnostics showed that both valves were open. 40 mile drive with the heater working as should and no cutting out either.

[X5Sport]

Fingers crossed

[marti]

For future diagnosis, if the ignition switch or CAS module is failing, check the vanity lights are working (sun visor lights) if not one of them is on its way out