Mondeo 2.0 Judder at constant speed

[Big N]

Hi All

I guess this is one that is bound to invite a myriad of different possible explanations, but here goes.....

OK, so its a 1998 Ford Mondeo 2.0 (Zetec), with 100k on the clock. Its behaved impeccably until now, and has been serviced regularly by competent individuals, but has just recently developed this irritating judder when "cruising" at constant speed, most typically at lower revs (35-50mph, 4th or 5th gear, so 2000-2500 revs).

Although probably the most likely area, I'm not actually convinced it's engine related - the engine idles beautifully and smoothly, fuel economy is fine (but not untypically high), and there's no funny noises. Acceleration is good, not jerky.
It's been doing it for about the last month / 1000-1500 miles

I've heard the lambda sensors are prone to failure, and can need replacing every 30-50k (and this one certainly hasnt ever been changed), but wouldnt that affect the idling?
The only other clue I can offer is that the cam belt has been replaced, but to be fair that was 6 months/6K miles ago, done by a Ford mechanic, so personally I doubt there's any link there.....

So the other thing I wonder - could it be transmission/drive related? But what?

Anyway, all ideas of possible causes welcome - though I'd prefer it to turn out to be one of the ones with a simple & cheap solution.

Cheers

 

[jonnyfishing]

It sounds like one of your front wheels has lost a balance weight,take it to a tyre bay and have the balancing checked,not expensive and only takes about 20 mins.

 

[Big N]

Hi Jon

Thanks for the suggestion, but its not the wheel balancing I'm afraid - my description wasn't clear enough really, hmmm, its more of a "jerkiness" than a "judder" (i mean, more random than regular) - and if you remove drive ie come off the gas and dip the clutch, then it subsides. Also if you stick your foot hard on the gas (clutch engaged, of course), then it also diminishes/disappears as you pick up speed. It feels more like some kind of "slackness" in the drive train somewhere, if that makes sense??

 

[Diyisfun]

I had similar problem, (although on the V6) turned out to be HT lead, Have you tried removing 1 at a time?.

 

[jonnyfishing]

To tell you the truth,it could be many things causing the problem.

I would first of all,try to establish if it is an engine fault.A strobe light would show any misfire while running the engine at the speed you quote.It could be a faulty plug,lead,coil pack,sensor or an e.c.u. fault.Best bet is to get it hooked up to find the fault.You could make a guess and start to change things,you could be lucky or it could cost you a small fortune and end up where you started.