Hi all, daily im becoming more and more stumped! my L plate 300 tdi 77k has a strange vibration/wobble/retardation like a learner driver kangaroo which happens when stationary and when moving mid rev rangeish resulting in loss of top end and mid range UMPPH.., ive replaced lift pump, run injector cleaner thru, bled fuel lines, changed all filters, examined hoses for delamination and still it does it! ive today checked the turbo for excess play and there isnt any more than about 1mm. when i start up there is the usual puff of black smoke then absolutely NOTHING smoking at all!! I have also today examined the boost diaphragm and found that it has a coating of oil , im aware that this is apparently turbo fail symptom, but if it is why is there no smoky exhaust? the air intake and manifold pipes have a very small amount of oil in but my research seems to say that this is not a problem. could the oil in there be something to do with the cyclone return pipe and not actually be the turbo failing?

Any help very gratefully received!

Update to this, checked wastegate today using airline and appears to be working ok, also blew air through boost hose and cyclone. The intermittent surging is still happening and I struggle to get over 60mph.

Still hoping for a guru to help!

I see (think this forum) someone had a similar issue and checked everything and it turned out to be the fuel pump setting, like it was tweaked in the past but turned back again too far

I had a similar thing with a 300tdi I had but at 3000 rpm it used to hesitate and not rev much more, I tweaked the fuel pump and every thing was ok after never found out why but I never had a problem after

If you go down this route make sure everything else is ok first

burgma1 said:

Update to this, checked wastegate today using airline and appears to be working ok, also blew air through boost hose and cyclone. The intermittent surging is still happening and I struggle to get over 60mph.

Still hoping for a guru to help!

Click to expand...

Help from our guru is by invitation only, don't worry, he'll be along soon, just after he's been tucked up for the night.

Thanks for reply, this problem suddenly started and not after any fettling, is it possible that previous tweaking (i kno that the fuel screw at top back of pump was adjusted slightly in may, not resulting in more smoke and all has been fine) has come undone of its own accord? Also did u have the oil on diaphragm?

Well im officially bewildered! Fitted new fuel tank to replace the slightly leaking one, and the problem seems to have dissapeared. As great as this is I cant figure out how it could have caused the initial problem. If only vehicles were this mysterious!!