Hi,

Last night I was driving home and as i slowed down my car started running rough. It was hunting badly, blowing black smoke and sounded like a tractor with a lumpy cam. at 1/4 or 1/2 throttle it would miss like a b**ch and the whole car would jerk but under full throttle it drove fine.

Was to dark to check anything other than making sure all the leads were on, so will investigate further when i get home tonight. Are these symptoms of any major fault? I'm hoping its just plugs, leads or a coil pack has given up. Just seems strange it will go fine under full throttle but not at part throttle.

I replaced the plugs about 2 months ago and do have a new set of leads at home to put in so will check the plugs and replace the leads. Any other suggestions greatly appreciated.

Thanks

The first thing I would check is your MAP sensor and the vacuum lines running to it. Any leak here will cause the car to run super rich and belch black smoke. Start spray is good for that: a vacuum leak will suck the spray into the engine and the revs will rise. At wide open throttle, there is effectively no vacuum anyway, so the MAP sensor will read (near) ambient pressure regardless of whether it's connected and working or not.

Failing that, disconnect one ignition lead at a time, working across the cylinders to find if the problem is isolated to one or two cylinders. If one cylinder is affected, it's probably a lead or plug. If two cylinders, probably coil pack.

Beyond that, do the same with your injectors, disconnecting one at a time.

Thanks, turned out to just be a hose for a map sensor

Cool. That problem pops up regularly on Fordmods.