Hi,

Stumbled across this forum and am hoping that those with far superior knowledge to me may be able to help with a problem I have!

I have a 2002 ST170 - got 97k on the clock.

For the past year, the car occasionally misfired - but only on long journeys and / or when the engine was very hot. The way to cure the problem when it occured was to drop a gear, and then slowly accelerate back up again.

A few weeks ago on a very hot day the misfiring was so bad it caused the car to stall. I called the AA out and they plugged their laptop into the car computer - no fault codes were showing. The AA man took a look at the car and believed the spark plugs and leads would need replacing. As he replaced them, he also discovered that the rocker cover gasket had split and was leaking oil into the spark plug wells - he said this would be the reason for the misfiring.

So I got the rocker cover gasket replaced (as well as the cambelt which was due). Picked up the car today and low and behold, after 2hrs of driving back up the motorway I could feel the engine misfire again. Only slightly this time, but noticeable. It is still there.

Straight onto the web when I got in and it appears this may be a common fault with the 2002 ST170's. The main problem is that it could appear to be any number of things!

Does anybody here have any experience of this problem and know what they did at the time to fix it?

I have an AA Warranty with the car so will be looking to get it fixed for free (fingers crossed!).

I should stress that when the engine is cold this problem does not occur at all - it is definately related to how long the car has been running on a journey and how much the engine has had to work in that time.

 

Almost defo electrical in nature not fuel, so the finger would point first at the most common thing being coilpack breaking down.
I would let the AA warranty take the car in as faulty, let them do all the guesswork, and spend all the money if I were you, it could indeed be loads of things, even leak leads even though new, silicone gel should really be applied to, leads that sit in hot places like this, down a well so to speak otherwise the can track chronically, unless you are using BOSCH plugs ?, if you are junk them and put ford/NGK ones in instead, famous for doing this on zetec, had it myself twice.
tabetha

 

would this misfire happen around 2-2.5k??.. mine does the same...apparently the PCM (power control module) needs recalibrating buy ford???

 

Thanks for the replies.

I'm not sure what make the leads are - I'll check.

I haven't really noticed what rev range it occurs at - I don't think it is specific to a certain range though.

I wish I knew more about cars for moments like this

 

Looks like the AA Warranty only applies if I breakdown.

Is the only option left to take it to a Ford dealer to get it fixed, or would a local garage be able to isolate a problem like this? Would rather not pay £100 just for Ford to take a look at the problem!