Weird problem with regular engine surges at higher speeds

[aargh]

We are having a weird problem with our Mondeo (diesel estate) at the moment and wondered if anyone can help?

Recently I've noticed that at higher speeds (usually around 50-60mph or more) the engine seems to be doing sort of pulses - regular surges and drops, as if the accelerator was constantly being pressed and released - around 1-second surges followed by the same time of lower power. It's audible and you can feel it, although it's not quite enough to visibly affect the car's progress (luckily!). Feels a bit like riding a cantering horse - leaping forward with each stride!

The car is a 2005 2l Mondeo TDCi estate. It's recently had a new flywheel and clutch (due to dreaded DMF issue) but the problem only started some time after that was done, so I don't think it's related.

Thank you!

 

[Peter.N.]

On the old IDI engines this could be caused by air getting into the fuel system but don't know if it applies to common rail engines, some have a pump in the fuel tank and some don't depending on the type of system, if yours doesn't that could possibly be the problem, otherwise it will probably an ECU fault.

Peter

 

[andy1020]

these diesel mondeos were prone to engine management related issues that Ford even struggled to sort at times.

Given the number of sensors on it and everything being controlled through ecu as mentioned I'd get it plugged in with a garage who has computer to read fault codes and see if something's listed.

Not an easy diagnosis that one I'm afraid though...

 

[aargh]

Thanks for the replies!

We suspected something related to the engine management, partly because the surging is so regular. Anyway it's going to the garage on Friday for an MOT and looking into this, so hopefully they will be able to figure out what's wrong...

 

[aargh]

Just an update for anyone who was interested or people who might be searching for info on the same problem in future!

The issue turned out to be with the EGR valve, which was clogged up. The garage blanked the valve as they said if it was replaced it would just clog up again in a while... and the problem disappeared straight away!

Thanks again to everyone who made suggestions.