The engine starts normally and will drive for hours with no problem and then suddenly start misfiring. Sometimes it’s possible to continue driving through it and then it’ll just cut back in and drive normally: other times it’ll cut out completely but, after 15 to 30 minutes and a few turns of the key, it’ll start up as normal.
Sometimes it’ll run for weeks, even months, with no problems but then do it for two or three days running. A lot of the time, the vehicle is only driven slowly on short trips so the problem isn’t that noticeable – but when towing, say, it’s really obvious.
So far I’ve had the fuel pump and fuel filter changed, I’ve cleaned oil out of the red plug to the ECU and recently had a new injector harness fitted and it’s still doing it. The vehicle has been on the diagnostic rig at a local independent specialist but, of course, it was running fine at the time so the technician found nothing!
Simon Greenwood, Crockenhill, Kent
Your investigations have been thorough, so I can understand how frustrating it must be for the problem to persist.
You’ve cleaned the oil out of the multiplug and you’ve even replaced the injector harness – which is often the source of the trouble. So, we need to look further. In extreme cases oil also gets into the ECU, via the injector and engine harnesses and the red multiplug, so open it up and check the internals of the ECU for signs of oil ingress and either have it cleaned or replaced.
If you’re at all unsure of what you are doing, don’t leave it to guesswork – have the ECU checked/repaired professionally.