Mondeo TDCi hesitation / jerky at ~50mph

[LocoBlade]

Hi All

My brother in law has a 51 plate Mondeo 115 TDCi auto which has developed a general lack of power throughout the rev range and a fairly severe hesitation / judder at around 50mph.

He bought the car up tonight for a quick check over the basics, and first thing I suggested was to disconnect the MAF and take it for a quick spin. Immediately it had more power and no judder at all so out came the MAF which had a quick a spray with carb cleaner before putting back in, even though it looked fine. That didn't help so the conclusion was to replace it, but whilst googling for a parts price tonight I found this old Honest John thread that seems to describe the exact same symptoms (albeit on 130 TDCi's) with the same "cure" when disconnecting the MAF, but when replaced the fault remained!

So, now we're back to square one really, he doesn't have a lot of money to throw at fixing it so doesn't want to spend best part of £100 on a MAF to find it does nothing, but I can't understand why the car would run so much better without the MAF connected if it wasn't actually faulty, unless by disconnecting the MAF you also disable another sensor somewhere or the ECU switches to a completely different mode which ignores other faults?

Any ideas or advice appreciated

[elliotff]

I have the same issue with my focus 1.8 tdci (2008). i have plugged in the OBD2 reader and found the fuel rail pressure drops from 18,000 ish to 4,000 if i accelerate above 50mph / 2700/3000 rpm.

I have has a quick call to ford and they say it is common for the fuel pump to fail ! could be the same issue i guess.

[elliotff]

I have resolved this issue by replacing the fuel filter. I didnt believe changing the fuel filter would make any difference.

I now have NO hesitation and the car is back to its original self!

Hope this helps

[LocoBlade]

Cheers and sorry for not getting back before, we had a fuel filter ready to change but things like the MAF were an easier test so when that came up with the results we didn't change it in the end. I'm not sure it's been done for a while so I think it's still worth doing anyway but I can't see this issue now being the fuel filter because I can't see how a disconnected MAF would cure a clogged or water filled fuel filter.

[chrislusty]

Clean out the EGR is another issue on these, easy to do but a messy job. Instructions can be found at
http://www.fordwiki.co.uk/index.php?title=EGR_Valv...

[Rich's Granny]

50mph equates to 1800 - 2000 rpm. very common issue causing hessitation/misfire at this speed is the EGR valve. As mentioned before it can be cleaned out which is a simple but very messy job. It will improve performance but may not completely cure the misfire till it warms up properly. Bit of a Mondeo TDCi trait.....

Depending on the age of the car you could fit a blanking plate on the EGR valve. If its a Euro 3 engine this will cause no issues but if its a Euro 4 it will put the engine management light on. Wont cause any problems but the light can be annoying for some..

[LocoBlade]

Cheers chaps, I'll suggest that as the next thing to try, what makes me reluctant to tackle that one (other than it being a bloody messy job!) is the MAF disconnection thing again, if it was the EGR why would disconnecting the MAF mask those symptoms so comprehensively? The only thing I can think is when the ECU goes into "no MAF mode" it might also stop worrying about emissions and not actuate the EGR?