More Zetec Killing Attempts Thwarted

 I decided the Stylus was all fixed & I could take it out, so started it up & noticed a small squeak in time with the engine such as you might get from a fan belt, I revved the engine, it seemed to be only doing it at idle, so assuming one of the butterflies was whistling, I set off gently. After a mile or so I could hear it over the engine, so turned round & took it home. I was concerned that the valve that had the bolt was slightly bent & was now rubbing on the valve guide - it seemed unlikely, but needed looking at.

After a little investigation it was misfiring too!

Fearing the worst I took off all the throttle bodies, re-aligned all the hoses that connect them & re-assembled it. It was now worse.

Oh good.

After a look around I wondered if the coil pack had given up & swapped it & the leads in a "jury rigged" fashion, it ran but was no better, but on re-connecting the coil pack on the car, I noticed the centre pin in the connector was being pushed back. I sorted that out & started it up again, It ran better, it was lumpy at idle, but seemed OK when revved. Then I noticed "smoke" from the exhaust, then realised it wasn't smoke, it was soot & walking round the exhaust side of the car, found a very sooty patch on the floor (no, it's not a panda skin rug).

I took one of the spark plugs out & that looked like it had been upholstered in black velvet!

I called my brother & we decided it was over-fuelling, the ECU won't over-fuel it, so it must be a sensor, there's only four, so not many to check.

Not the Crank Position Sensor as the engine ran, Not the Inlet Air Temperature as that defaults to 20C, the hose to the Manifold Absolute Pressure was all connected, so......

<--- Throttle Position?

That'll be it then!

Clearly I had inadvertently pulled the wire out when fiddling with things under the throttle bodies & a little investigation revealed that all three wires were badly crimped. The ECU was being told the throttle was wide open & fuelling accordingly.

So the connector was taken apart & the wires soldered on to the terminals, re-built, bound in loom tape & re-connected. It now all seems to work nicely again.

And the squeak has gone, so that must've been a tiny air leak at the hoses.