Old faithful 03 plate StiloJTD not running too well on way home last night, engine suddenly feels really lumpy 1200 - 2000rpm, not great power, but goes OK when you put the foot down up to a point, checked injectors, vac lines, egr defo' not problem cause it's blanked, been getting engine warning light @ around 3000 - 3200 RPM when accelerating hard under load (eg going up hill) lately so decided (while under it this morning anyway) to move the turbo overboost control valve up away from all the road spray n crap & re-piped the vac hoses, the waste gate actuator looks OK not losing vac / is moving in & out when I pull the vac line off, but still getting same warning light when putting the foot down under load, sure this is overboost? so valve might be goosed, TBH I'm not really sure how this thing is supposed to behave - you cant see it under load & drive at the same time; wonder if this valve could cause a lumpy running at low rpm? feels like running a cylinder down but when I pull off each injector cable a massive difference - not not an injector, might just be a batch of poor diesel? so put in some posh v-power diesel & some injector cleaner & have taken it a run up the bypass giving some juice - made no apparent difference, went well enough with the pedal to the floor but then back to running like a mini dump truck at normal driving speeds at 30 mph 3rd or 4th gear.
I'm now thinking diesel filter (power loss) or Crankshaft sensor (lumpy/timing related?) Any thoughts, think I'm on the right track here?

Mate if you've got an engine light then you want to be reading that to check what it is - that's probably going to be a good clue.


Wouldn't surprise me if you've got an air leak or a MAF issue but check that fault code.

Ok so a diesel filter is ordered - along with an oil & air filter which I'll likely just change at same time.
But after driving it to drop the wee one off at school this morning........I've had a bit of a brainwave.
I'm beginning to think the timing has jumped a tooth. Getting away from the point about the engine light, & bearing in mind that there's
no engine light on at minute & also no fault whatsoever reported on OBD. Now the engine light has only ever only came on during what is now very clearly an 'over-boost' condition; then it goes straight out again; I know that this is a pre-existing fault anyway & certainly predates this new fault by a very long time; plus it's not even a real problem for me b'cause my engine rarely sees 3200 rpm anyway; so has been easy to live with - the reason I mentioned it is that I started off investigating whether it's linked to this lumpy engine issue, it is not.

The actual problem is that despite the engine appearing to run fine at tick over, it is running lumpy like a two cylinder mini dump truck at 18oo rpm (ie my normal cruise rpm in most gears) - now I know all cylinders are firing b'cause I verified this by pulling each injector plug off individually. To me, this looks very much like valve timing is out - hence I've started now to focus on timing belt. Engine is 110,000 miles, serviced by me every year, never uses drop of oil & normally pulls; well, like you'd expect the 115bhp TD to.
I last put a belt & tension-er on it at 68,000miles.
This is a sudden thing that's just happened the other morning.

I'll go out;(If this ruddy rain ever stops) & I'll remove crank - pulley, alternator belt & covers & inspect the timing marks, the belt looked OK when I had a quick look to judge general condition but I never checked every tooth present, so I'll do this as well; apparently teeth can strip? Now I struggle to see how this can happen, unless a good few teeth are stripped off the belt - but there's some info on other net forums (for other cars) suggesting that a slippage event can happen whilst belt going round the small radius of the main crank shaft toothed pulley? - anyway, one way or the other, I'll now be putting a new belt & tension-er on it, I'll update the post with any findings.
Going to leave it & not drive it either, till over weekend & hopefully it will dry up out there.
Meantime, any input from anyone who has actually seen the effect of a belt slipping a tooth or two is welcome.

OK so been out this afternoon, removed aux drive belt, crank pulley, covers & got into the timing belt, have established that nothing has moved & that the belt is in generally good condition.
I could see that I had made my own very definite punch mark on the block first time I changed the belt; corresponding accurately with the existing mark on the crankshaft pulley; when everything aligned correctly at TDC. This is all still spot on when camshaft mark is aligned with the pointer on the housing.
So back to square one I'm afraid. As I said, no engine warning light & the ECU is reporting nothing.
I still intend to fit a belt-tension-er + water pump kit in near future - but really need to get to bottom of this first - It just feels like timing, I can't imagine it being something mechanical. I wonder what could make the engine suddenly seem out of balance at cruising rpm despite running like a sweetie at tick over- a problem which has just appeared out of the blue? Been right back through all the wee vac pipes & found nothing. MAP sensor seems fine, MAF sensor seems fine.
I have even considered if it could even be related to the flywheel (timing) sensor, I recall changing one a few years back - however the symptom back then was a very sudden loss of power or failure to start (different completely from this), anyone ever had symptoms like this for anything else. What's this dual mass flywheel & does anyone know if the Stilo 2003 JTD 115 has it?

Have you checked the turbo plumbing for air-leaks?


Have you pulled the glow plugs and checked them with a set of jump leaks or something?


Your overboost issue is an issue - without wanting to cause offence honestly I think you'd be a fool to ignore it. The symptom you've got is overboost, which is what the car can measure and report, but actually what that needs to be telling you is that your car is failing to control it's boost pressure properly. So that could mean that your AFR is all over the place. MultiECUScan is able to plot you some graphs that might help show you want the car wants vs what the car has.


If the AFR has been out for a long time you could be sat there with a blocked cat for example - which would potentially explain your problem.


I'd consider checking for air-leaks in the boost system next. Give the intercooler a good check too. Lord knows how but I've had the case before now that a stone managed to fire through the little vent duct on the side of the bumper and hit with such force for a small object that it pierced the intercooler with a hole not much greater than a grain of rice.


here is what the plumbing should probably look like:

Thanks for your advice, it is much appreciated. I've allowed myself to consider too many possibilities at once here, of course the idea of diving in needlessly changing a flywheel on a 03 plate car is a job that's less than appealing, that said, the the car is solid throughout, having been kept mechanically sound & under-sealed every year, so it has a fair worth to me.
So bearing that in mind & focusing on your point about the turbo plumbing being the first route you would go down, I've now got fuel, Air & oil filter, so I'll spend my next set of days off with it up on ramps & remove inspect/ refit all of the pipework & plumbing concerned. I do see a lot of info online relating to the fact that a turbo (on whatever model of car); often comes online around the sort of rpm where I'm having issues - I don't know enough about the actual fueling / control side of modern ECU controlled turbo diesels - I'm a spark/maintenance fitter by trade but with cars, general electrical faultfinding & plenty of spannering is admittedly more my thing. The diagram attached is same as my car.

Not sure about the glowplugs - it just to test them? I do have 3 new glow plugs lying as I changed only one last year (which was open circuit) so it would be an idea to go in & replace other 3 - although motor starts no probs even on freezing morning.
I have a wee basic handheld OBD scan tool but I'll check out info on multi ECU scan.
I'll update on the check of pipework.

If your going to be checking the pipe work check the large hose number 2 in previous diagram as it runs behind nearside (uk) wheel arch liner and is know to rub against the arch liner and cause a hole in pipe, when doing some work on that side of mine I cable tied a piece of rubber laying about in shed on to the area where I could see it rubbing to give it a little protection from it happening as I noticed it had been in contact with the arch liner, if you just remove the front screws of the nearside arch liner you will be able to have enough access to check the large pipe at that point, though usually you can hear if there is a large leak there but still worth a check.
Glow plugs would only effect any cold starting problems, which sure you would be aware of.