Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing zetec 1.8 misfire

I have an intermittent cold misfire on a 1994 4/4 silver top zetec 1.8. It is not damp related and the plugs were changed last year. The misfire stops after a couple of miles and the car runs well then. I was thinking coil pack, HT leads or one of the sensors. Any ideas?
John

When you say misfire do you mean it runs rough for the first couple of miles or does it keep missing intermittently?

I never had such a misfire on my 1.8 Zetec but I think I might have started by checking the coolant temperature sensor. It's on top of the thermostat housing at the rear of the head on the passenger side (RHD).

It very cramped around there and the wires are squashed under the heater pipe which could have chafed it and damaged the wires.

The reason I say that is because the ECU takes a coolant temperature signal and enriches the mixture until the engine gets up to running temperature.

If that has failed, it will default to the warm running mixture which will be too lean while the engine is cold. A bit like running an old carburettor engine without the choke.

If the wires look intact of course it could be a sensor failure but they are normally reliable.

Could be a host of other things as well but that's where I would start my diagnostics.

Thanks for your quick reply Bob.
To clarify, it sometimes runs rough for the first few miles but on other days it runs just fine. As the engine temp rises it always runs ok.The car always starts immediately on good or bad days! I will check out the sensor wiring next as you suggest.
John

I had a similar problem with my Zetec 4/4 it was solved with new plug leads obtained from Burton.

Regards
Nigel

Thanks Nigel, I will try that next as the wiring for the thermostat sensor looks good with no sign of chaffing. I may get the coil pack from them as well, just in case!
John