About 2 months ago I was called out to a Ford Mondeo taxi with what appeared to be a significant misfire. I can't remember which DTC's were present at the time but I replaced the spark plugs followed by the ignition leads then the EDIS coil which fixed the problem.

2 weeks ago the car started misfiring again. There were no DTC's present but looking at OBD Mode 6 data I could see cylinder 2 with a percentage in the misfire column, the other cylinders being 0%. I swapped the spark plug then the fuel injector with cylinder 1 and the misfire remained on cylinder 2.

On Friday the PCM logged P0302, the first time I'd seen a fault code since the misfire returned. I changed the ignition leads again (with a new ones of course) which made no difference then replaced the coil which fixed the misfire.

This morning (Sunday) the car is misfiring again after less then 36 hours. I've just come back from the car and it's logged P0300, P0302 and P0303....random misfire, cylinder 2 misfire and cylinder 3 misfire.

It could well be the new coil is defective but I'm also concious that this could be a problem with the PCM coil driver(s).

I'm going to replace the coil with an OEM Ford one tomorrow but I'm seriously thinking of sending the PCM away for testing.

Any thoughts or suggestions would be much appreciated.

Evening Jonathan,

At the moment we don't know if the misfire is ignition, fuelling, or engine related. I have a "thingy" which I plug into the plug lead which can determine whether an ignition misfire is caused by either the coil or lead. If ignition related, is it possible to scope the signal from the ECU to the coil-pack? What plugs are you using? I assume vehicle has correct 5w-30 oil. Compressions? Emission figures may be of help also.

I do not remember seeing ECU problems on these except the earlier models where an ignition misfire has spiked the ECU.

I can remember one case a year or so back when I diagnosed a faulty coil pack. Customer fitted a new one but fault soon returned. Customer had overtightened the new coil pack to its metal base which caused a hair-line crack. Found that by accident because I removed the coil from its fixing plate and misfire stopped. Coil HT was earthing to the metal plate.

Rgds

Pete M

Morning Pete, thanks for your reply.

Over the last week I've had it on the gas analyser and conducted a BET Test which it passed with flying colours.

I've also had a Launch CRecorder installed for 24 hours which showed up nothing of interest.....not even a DTC.

It was serviced not that long ago by myself and has 5W/30 fully synthetic oil in the engine and I only use NGK plugs which are the correct part number.

I'm going back to it for a couple of hours today to run some more tests including cylinder compressions and a manifold vacuum check which I didn't have time to do last week. I've got a dual-channel scope and will scope the primary coil signals from the PCM and post the traces on here for reference.

I forgot to mention in my first post; the misfire is only present under load and isn't evident with the vehicle stationary at idle or when the engine speed is increased.

Jon

Hi Jonathan
I had one of these in last year and it turned out to be a restriction in the fuel pressure caused by a blocked fuel filter and lots of crud in the tank. The symptoms were misfire/hesitation under load and at high engine speed but only on the road.In the garage it ran fine.
HTH
Allan

Hi Jonathan,

"I'm going to replace the coil with an OEM Ford one tomorrow"??

You havn't been using Intermotor of Fuel parts replacement parts have you?, If so , that is probably your problem, OE leads and coil would be my way forward.

I have to agree with Tony, I wouldn't fit anything but genuine parts on any ignition system nowadays. I have changed so many coils for garages that have fitted these 'OE quality' coils from the makes that are mentioned and I could name a few more that are just as bad in a different colour box. Sometimes these have caused ECU damage after fitting where as the original problem would have just needed a genuine coil to cure it. I have even had a Bosch coil that didn't work out of the box for a Golf. What was interesting is that it said 'Made in china' and had been picked up from Bosch in Denham so if that's not a moody part I guess the quality has gone out of the window with their parts as well. What'll bug you now though is that Ford will probably supply a Bosch/FoMoCo coil as was the case with a Puma I changed one on last week.



Liam

Evening all,

Thanks for your time replying.

The owner supplied all the parts which were standard aftermarket stuff from the usual sources. I can't remember what make the last coil was but quite probably it was an Intermotor given what I remember of the box. The previous replacement coil and the HT leads were supplied from what I consider a lower-end national aftermarket supplier.

I fitted an OEM Ford (FoMoCo) coil this morning and all was well again.

I checked the compressions at WOT with the coil primary plug disconnected and each cylinder was fairly well balanced at 210psi-215psi.

I'm now in two minds as whether to risk it and return the car or to send the PCM away for testing. The owner has given me free rein on what I do next so I'll report back tomorrow.

Thanks again,
Jon.

Hi again Jonathan,

My rule is for anything post 2001 you MUST use genuine parts, if the customer turns up with some crap he has bought off e-bay or the two makes I mentioned earlier send him on his way and do his own repair !

The number of times I have seen P0420 "cat efficiency" codes from garages fitting rubbish Chinese copy parts to post 2001 cars makes me laugh as,the car then has to go back in, another crap copy part is fitted and lo and behold it is back within a week and a half with the same fault code, a bit like your experience.

I hope you learn from this, your time is money you are losing.

Hi Jonathan,
Just want to add my vote to Tony and Liams sentiments, fit only genuine parts unless you want to see the car again.
The one good thing is if the customer supplies the parts all your labour is chargeable! Don't keep swapping dodgy bits for more dodgy bits supplied by the customer for nowt.
Regards, Shaun