Hi all new to the forum so looking forward to hearing from you all. Straight into it then I've got the 1.8 tdci focus estate which has started developing a strange fault over the last few weeks. 

Casually cruising along in any gear at around 30/40mph and the car has started "snagging" I suppose. A momentary loss of power for barely a second or 2 then comes right again. Sometimes barely noticeable other times she jerks a bit. I've had the diesel filter and air filter changed and a can of injector cleaner in the tank ( no idea what it was called but cost me £20 with the garage) which doesn't seemed to have done an awful lot. My average MPG has dropped from around 42 to about 34 aswell.

I'm praying this is not an injector fault and my local garage doesn't seem to Think so. No rough idle, no difficulty in starting. No fault codes on 3 different diagnostics, No smoke, no smell of diesel etc etc just this. 

I did notice last night that whilst driving around a roundabout that the esp light was on and lost throttle until coming off the roundabout (bare in mind I had no loss of traction was no where near fast enough and have just put 4 new tyres on ) 

Not sure if its worth mentioning she's an ex cop car from Devon and Cornwall serviced every 6 months up until I bought her summer just gone.

 

Hoping someone could shed some light on the matter before I go and workout £££ trying to find an intermittent fault

How's the turbo? Does it seem to work when this happens?

Can't remember what turbo those engines have but on my dad's VW bora 1.9 TDI, the turbo veins used to stick causing a lack in power before the veins would move again giving the power back. He used Mr muscle oven cleaner which did fix the problem but first need to see if its the turbo sticking. 

Turbo seems to be good as far as I can tell. Never happens under load ( ie when putting the right foot down lol) only ever seems to happen momentarily when at a steady speed or occasionally when pulling away. How would I go about checking these veins you speak off ? Not entirely sure what or where they are lol. Thanks 

4 minutes ago, Jayykarr said:

Turbo seems to be good as far as I can tell. Never happens under load ( ie when putting the right foot down lol) only ever seems to happen momentarily when at a steady speed or occasionally when pulling away. How would I go about checking these veins you speak off ? Not entirely sure what or where they are lol. Thanks 

Same engine as mine, the turbo is VNT (electrically controlled) so the ECU would almost certainly know (and throw a wobbler/error code) if the VNT wasn't responding quickly enough.  Siemens did supply a large batch of bad injectors for this engine but your sig says your Focus is 2007 which is before this happened and the injectors on this engine are otherwise very reliable.

 

Interesting that your ESP light came on as traction control was only an option on the pre facelift MK2, I know mine doesn't have it.  If the engine is not smoking or otherwise misbehaving mechanically, maybe the issue may be with something like the TPS i.e. if the ECU doesn't know how much throttle is being applied it will probably default to idle as a safe fall back.

Hi Damien, thanks for your input. Car definitely has esp, got the button on the dash (ex police car so maybe that's why lol) only ever seems to happen on one particular Round about atm so perhaps a coincidence. As for the TPS I must admit I hadn't considered that. I've had a Delphi system plugged in but only threw up 2 old codes for an exhaust sensor. Cleared those and nothing has come up since. Had the mechanic in my local drive the car up the road with comp plugged and although he felt the jerking it did not throw any further codes... strange to say the least. Other than this little bugbear the car runs a dream. Never fails to start no smoke etc etc so really not sure now lol.

Forgot to mention aswell in case this makes a lot of difference it only ever does it when engine is up to temp. Never when she's cold.

Anyone have any suggestions. Problems appears to be getting worse so I'm starting to get worried lol

Anyone out there ?

Unfortunately I've not got any further suggestions.  Maybe @iantt or @stef123 will have some suggestions as they're 2 of the more knowledgable members on here.

Haven’t got much to go on really.

would you describe the power loss comparible to when the ESP kicks in? 

Hi @stef123 sprry for the delay in responding never had a notification for your reply just happened to check the site by chance. No when the esp kicks in its feels like the power is capped i guess, this is more of stutter the car is quite jerky for a that 2 or 3 seconds then right again. Only ever happens at lower speed around 30/40. Took a 2 hour drive up the motorway last night and same back again didnt do it once on the motorway but soon as i got into town at lower speeds she started again. Local garage is at a complete loss. Changed the diesel filter about 3 months ago and the air filter last week but still no improvement.

I wish you were closer, I’d have liked to take a look at it. 

Just fixed a 2015 Fiesta with I guess, a similar issue in some respect - although yours doesn’t have a lift pump. Fault would only happen at low speed and not on motorway at constant speed. Long story short, but of diagnostic tracked it down to a bad connection on fuel pressure sensor. 

The guy who owns the car put it into a garage who couldn’t locate a fault and wanted to change the low pressure fuel pump.