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unhelpful fault code

Just taken a look at a Mazda Premacy petrol. Running on three, engine management light is on.

Plugged in code reader : 0300: cylinder misfiring.

Thank you very much :)

No idea what the fault actually was. The car had just come from an auction, obviously someone had recently worked on the car as it had one new coil and new Bosch plugs. No cylinder appeared different to any other, compressions were good. No inlet leaks, everything plugged in. I checked all the resistances in the coils and leads were sensible or similar, but replaced the two coils the other way round, so that the new coil now had the short plug lead. Ran perfectly, light stays off, scratches head. mutter, mutter. Gave it back and said try that.

Reply to
Mrcheerful
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Dodgy LT lead, making contact now you've moved things around?

Reply to
Newshound

Possible, nut I would doubt it was that, simply because a LT fault would shut down two cylinders, while this was definitely on three. A real head scratcher, I have wondered whether maybe I disturbed one of the injector connections, that could acount for running on three and that the plugs all looked the same colour with none of them wet.

If it does it again then I might work out a way to short each lead to earth to try and narrow it down to one cylinder.

Reply to
Mrcheerful

Agreed, didn't know if it was two or four coil. In the old days we'd just pull the plug caps off one at a time! But last time I had something like this I unplugged them all and left them resting in place, then disturbed them one at a time with a suitable well insulated tool to identify the dead cylinder.

Reply to
Newshound

this is quite unusual, it has two coils, but one plug cap is attached to each coil, then each coil has a plug lead, one long one short. The coils are bolted to the head. So the only way would be to attach an extension lead to the fixed plug cap . The plugs would have to be shorted out individually as lifting one cap would make the spark for two cylinders disappear! At present the car is running great, so hopefully that will continue :)

Reply to
Mrcheerful

Ah.

If it ain't broke......

:-)

Reply to
Newshound

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