.... It's happened at start up and at normal road speeds, revs fluctuate wildly and power drops off. Restarting sometimes clears it, .....
.
This means its NOT the mechanical throttle body/throttle valve
Not unless the fly by wire throttle, if you have one, isnt having a mad dance randomly opening and closing the throttle. ..I think they design them not to be able to do this. not sure though.
.
.... How can they make that call if they don't know what was wrong with it in the first place? Usual dealer workshop try on I suppose.
.
Yeah ...pants answer that is ...what a bunch of fitters,
... you need someone with a brain as DF suggested.
Other stuff Ive thought of is the FI pressure release valve (return valve or similar) is failing and loosing pressure occasionally...they don't usually fluctuate though...but you would lose loads of power all of a sudden, like lifting the accelerator in feel? ..if it kicked back in again (which could happen I guess) then the engine could surge as if you'd stamped on the gas again, which id guess is what you would be doing in that horrible surging situation. .... The fuel pump powering down and up again would also have the same feeling.
The fact that switching it off and on again often corrects the fault does lean me towards an electrical fault, wee tiny sparks between those pins in the connectors can suddenly stop the flow by sooting up, then just with a shake of swithing off or another spark, or just the surge of new power can connect them again, or all in reverse of all that, either way you tend to get an almost magical hit and miss effect thats so very hard to nail down. ...
.
Problem started again yesterday. The car has been running normally this afternoon - no warning lights showing - but I don't trust it and the fault could show up again any time. I'll do a bit of phoning around tomorrow, but we live in a rural area and there's not much choice of workshops. I appreciate all the advice.
From all Ive searched this last half hour, it seems as if the wiring and connectors to the throttle position sensor and other stuff around that harness spot, are mostly THE FAULT!!... hence the ford suggestion of a newly improved replacement of the whole area with new parts, all with improved gold plated contacts in a desperate attempt to correct the fault in a reliable way.
If your engine was in front of me id want the fault to show, then id touch and wriggle individual connectors until it corrected, (starting around that throttle sensors wiring section ).... OR in reverse, untill it disconnected and made the engine run badly . ..if you do this methodically you should be able to pinpoint exactly which connector block is at fault. (maybe more than one) ...WD40 is the perfect contact cleaner, usual way is to unclip and re-clip repeatedly with wd40, as the action of pushing it in and out helps to clean the corroded pins off. ...note what colour the electronic pins are, if they are blackened with soot because they been sparking this can take considerable scrubbing to clean it all off ... unfortunately you cant scrub the female parts of the connectors as they are down a slot, so just wd40 and re-clipping repeatedly is the only way.
...
Does that mean then on a modern car that you can't pop the bonnet and operate the throttle like you can on older ones? I'm a complete div when it comes to modern car engines/electronics btw, it's all far too complicated for my liking.
They still have the same throttle ( throttle types) with fuel injection so in essence its very similar.... however as your thinking they probably wont have a leaver on the outside to physically twist.
Cable or not though, its fuel injection fuelling, so it must have a throttle sensor somewhere to give information about how far the throttle was turned, from what starting point and at what speed...blah blah
