TD4 lack of power and occasional MIL lamp

Hi all, started having a problem with my car. It occasionally lacks power and almost stalls when the clutch is down (changing gear) or when idling and the MIL lamp occasionally illuminates on the dash. Not had chance to get it into a garage to see what (if any) fault codes are present. It's had the fuel filter replaced (was doing it before) which has made no difference. I'm thinking maybe the fuel pump in the rear wheel arch??

Any thoughts?

sounds feasible....

Quick update,

Just replaced the fuel pump and the car is running better at idle and revs well whilst stationary with no MIL lamp Going for a test drive after dinner to make sure all is well.

Been for a test drive and all seemed well to begin with. Good acceleration (Synergy 2A on setting 10), after a while I lost power around 4K rpm (whilst booting it) and the car lacked power throughout the rev range after that point. There was loads of blue smoke out of the exhaust whilst coasting and reving. I stopped and then restarted the car and drove it sensibly, no more blue smoke from the exhaust and it reved and accelerated as it should.

Any ideas? Boost valve playing up???? Overboosting and then limiting boost throwing out fuelling???

I double checked the Synergy power setting and it was only on setting 7, the car was extremely torquey for such a low setting.

You checked your turbo hoses for splits?

DuncanS said:

You checked your turbo hoses for splits?

Click to expand...

Yeah I've checked them, I replaced them with silicon hoses about 12 months ago too.

If I drive sensibly it drives ok. There is definitely a misfire when idling though which considering the mileage, it's probably due an injector or 2.

There does seem to be massive torque from very low down which was not there before. Now that could partly be down to the previous fuel pump struggling to supply enough fuel and I might be chasing a red herring there but it did seem strange that it cut power around 4K when I was booting it. I'm assuming that the ECU monitors boost pressure and in an overboost situation cuts the boost resulting in massive overfuelling like I had on the test drive. Once I turned the engine off and back on again all was well driving sensibly with no blueish smoke.

Been on a 40 mile drive. For the first 20 miles the Synergy was on setting 10 (pierburg MAF fitted) and with gentle driving I could hear and feel the car misfiring. On the return journey I set the Synergy to 7 and couldn't really feel or hear any misfire. When I got home I let the car idle for a bit and the revs were rock steady a tad over 750rpm. I'm sure the reduced power setting is just masking the problem.