tzd turbo cough/splutter

[rutter123]

occasionally usually when the engine is cold i get a misfire/cough/splutter just before the turbo kicks in, this tends to happen at about 2000-2200rpm, not had this b4, once warm it dosent happen at all and all is well apart from this. have noticed a bit more than usual grey/black smoke from the exhaust under heavy right foot, have checked all the pipework and nothing seems amiss.dont think its the fuel pump as its only 70k's old, dosent seem to have got any worse just the occasional cough, mileage is 265k and as far as im aware its on its original turbo. kkk turbo, lucas pump, i dont suspect the glows either as car starts ok with no misfire or the injectors as these were cleaned at 200k

thought it could poss be a case of a bit of dodgy diesel but need to run the tank empty first. there are no signs of water/dirt in the filters.

any ideas?

[KevR]

Sounds like something's making it run a bit lean - possibly still running lean when it's hot but you don't notice it so much, in the same way a carb-fed petrol car will run a bit lean when hot without too much problem but run like a pig when cold. I'd run through the usual suspects anyway - water in the fuel filter, air in the fuel lines, sticky pivot where the anti-stall and cold start arms pivot on the same shaft etc.
Would also check the boost valve in case it's clogged up with oil from the intercooler (the higher mileage, the more likely). I've fitted a cheapo fuel filter between the intercooler and the boost valve on mine, as the last couple of boost valves I've taken apart have been utterly clagged up with black, gooey oil residue. In fact my money's on the boost valve as when it's not working at all you get that kind of symptom (hesitation) all the time, and when it's adjusted a bit lean it happens occasionally. I suspect that when it's all clagged up, it doesn't work very well at lower manifold pressures, then perhaps over-compensates when you really stick your foot down.

[rutter123]

kevr, second paragraph seems to be a probable cause, certainly symptoms of, i have a good spare complete kkk turbo (which came from a t/d with less than 80k on it) of which i know has a good clean boost valve on it and is ready for fitting hould i need it tho today i bypassed the cav type fuel filter with a simple in-line filter and hey presto no splutter??? will run for a few days and see how it goes.

[KevR]

The boost valve is on the pump, not the turbo.... follow the small diamater pipe down from the front lower edge of the intercooler to the front lower side of the pupm - there's a bit sticking out of the pump, and that's the boost valve. The wossname on the turbo (wastegate actuator?) can stick, but I'd say the boost valve is the first port of call.

[rutter123]

Have bypassed the cav type fuel filter with a simple inline filter which seems to (for now anyway) eliminated the problem. Hopefully.