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Zetec misfire or something else?
Alan_Thomas - 13/3/06 at 11:31 AM

1600 Zetec running Fords ecu and 'Stanard' ignition etc.
Suddenly only running on 2 cylinders. Can pull off number 2 plug lead without changing rough idle. Replace that and then pull off number 4 plug lead no change to rough idle. However pull off 4&2 and engine stops.
Thought Coilpack! - changed but exactly the same.
Any ideas anyone?

- Alan

stevebubs - 13/3/06 at 11:43 AM

Blown driver in ECU? those coilpacks pack a lot of current backlash into the ECU.

stevebubs - 13/3/06 at 12:41 PM

Also worth checking for sprained wiring / plugs between ECU and Coil pack

greggors84 - 13/3/06 at 01:03 PM

Same happened on my little brothers Zetec SE in his fiesta. I was driving in at the time, changed the coil pack and no difference, but put the coil pack in my mums maverick and it was misfiring too, but not as bad.

Even though the SE and the E are different engines im sure they use the same ignition systems

Ended up getting an auto electrician we know to have a look and he found out it was the ECU, was £200 to replace!!, bought a new coil pack off ebay for about £40 and it all worked fine again.

About a month later the coil pack went again, luckily it didnt take the ECU with it, found out ford have released a new coil pack, so went to the them and managed to get it for about £55. Stuck that in and has been sweet since.

If your ecu has gone probably worth changing to megaspark/squirt as will be a bit cheaper and you have the full map-ability, for upgrades.

EDIT: Just saw steves second post, the wires going into the coil pack were a bit bare on ours too, definately worth covering up.

[Edited on 13/3/2006 by greggors84]

britishtrident - 13/3/06 at 02:57 PM

I have seen the coil pack bring down the ECU on Fords also.

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Note most manuals now advise against pulling plug leads off as it can create voltages that damage ignition system electronics.

stevebubs - 13/3/06 at 03:34 PM

quote:
Originally posted by greggors84
Ended up getting an auto electrician we know to have a look and he found out it was the ECU, was £200 to replace!!, bought a new coil pack off ebay for about £40 and it all worked fine again.


There's quite a few second hand ecus on fleabay at the moment....

MikeRJ - 13/3/06 at 06:09 PM

quote:
Originally posted by Alan_Thomas
However pull off 4&2 and engine stops.


That is expected and entirely normal behaviour, cylinders 1 & 4 share a coil, and so do 2 & 3. Removing the HT lead from a spark plug will stop the other plug that shares the coil from firing, so remove 4&2 and you also stop 1&3 from firing.

It's not really possible to diagnose misifring cylinders like this as you could with a distrubutor based system, though your experiments seem to confirm that one cylinder of each coil pair is running, which is a good indication that the coil pack is ok.

Try checking exhaust manifold temperatures, the misifiring cylinders should be much cooler (esp. if you have a proper tubular manifold rather than a stock cast item). Obviously poking the manifold with a finger is a pretty silly thing to do, so just try a couple of drops of water, the running cylinders will vapourise it very quickly.

If there are no obvious electrical faults, a compression test would be next on the list of things to do, to eliminate a head gasket failure or burnt valves etc.

jollygreengiant - 13/3/06 at 06:46 PM

I take it you have tried checking/replacing the even more obvious plugs and leads first.

rusty nuts - 13/3/06 at 06:56 PM

Have you changed the oil lately? Zetec engines should run on 5/30 . Incorrect oil plays havoc with the hydraulic tappets and can cause rough running.

britishtrident - 13/3/06 at 07:07 PM

quote:
Originally posted by rusty nuts
Have you changed the oil lately? Zetec engines should run on 5/30 . Incorrect oil plays havoc with the hydraulic tappets and can cause rough running.



Should go away after the engine warms up, 10w/40 was the original spec but they changed it ot 5w/30 when the hydraulic tappet was diagnosed. Rover engines also run a lot better from a cold start on 5w/30 or 0w/40.

Alan_Thomas - 14/3/06 at 03:11 PM

quote:
Originally posted by jollygreengiant
I take it you have tried checking/replacing the even more obvious plugs and leads first.


Thanks for all the feedback
Had already changed Plugs, leads and now coilpack.
Used a set of those 'ignition testers' that flash when the plug fires and all appeared to flash normally when cranking.
Oil was 15/40w until last service when I changed it to 5/30w semi synth which is the recommended.
With regard to tappet Jacking I thought all Zetecs from Focus cars had solid lifters and only earlier zetecs had hydraulic lifters.

Looks like a visit from an Autoelectrian is in order.
Steve - You are, like me, in Reading can you suggest anyone local?

- Cheers Alan

stevebubs - 14/3/06 at 08:48 PM

Not off the top of my head.

If you have time, pop down to Wokingham MOT (by Pearl at the Woosehill Roundabout) and ask for Craig.

Tell him the guys with the Red and Yellow Furys sent you, and is there anyone he can recommend.

Top place for an MOT, BTW...very kit car friendly (as is the CNC shop next door)

(Oh and from my experiences, avoid Prince Bros in Twyford)

[Edited on 14/3/06 by stevebubs]

stevebubs - 14/3/06 at 08:52 PM

quote:
Originally posted by Alan_Thomas

With regard to tappet Jacking I thought all Zetecs from Focus cars had solid lifters and only earlier zetecs had hydraulic lifters.



All "silvertops" are hydraulic, and "blacktops" are solid.

stevebubs - 14/3/06 at 09:00 PM

One other check I would make is the crank sensor wiring.

Just remembered that when I originally wired up my Emerald, I used a connector that seemed ok. However the engine was prone to intermittent misfires on cylinders 2 & 4 (proven by the the exhaust manifold tube temperatures - my IR temp gun has just packed up, though )

Took me 2-3 weeks of fiddling to figure out the problem...Changed this plug and all was well.

Of course, it may even be the crank sensor itself...


[Edited on 19/3/06 by stevebubs]