I have scanned the forums and there are similar threads but not quite the same I think. I just need a little advice or hints to focus on first on what maybe the issue.


My stilo 1.9 JTD is hesitating and losing power from cold. Mostly at low revs such as when at a junction and pulling away or worse; having stopped on a hill. It also feels a bit lumpy driving.


Once it has warmed up say 1/4 way it seems to be fine. Also from cold when revved it puts out white smoke.

I have a mechanic friend who is going to plug in his Bosch diagnostic computer when he his free but they are not always clear indicators.

I am leaning towards it being a stuck or blocked EGR valve or maybe MAF sensor issue.

I know some blank the EGR but I read this throws fault codes up in the ECU.

Advice ?

Blanked the egr on both my stilo’s JTD 115 bhp no fault codes and car was much improved, quicker with less smoke and the hesitation/ power loss was gone.
The only thing is you need to rev it hard before the MOT or it will fail on immisions.

Glow plugs??

My old 110 was like that.

Started ok for 2.5 yrs with bad plugs.. but with only 2 or3 warm cylinders it wasnt great.

Snowy winter stopped it dead..



The white smoke is unburnt fuel
For whatever reason..


as you say.. getting revs.up will get the cold cylinders combusting their fuel efficiently

Unburnt fuel would be black, white is water. It could be just condensation in exhaust.
Try to remove EGR and look at it, it's not hard. You can check MAP while you are there. (If you have 85kW it's just under EGR, not sure about others)

roll said:

Unburnt fuel would be black, white is water. It could be just condensation in exhaust.
Try to remove EGR and look at it, it's not hard. You can check MAP while you are there. (If you have 85kW it's just under EGR, not sure about others)

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Poorly burnt fuel (from overfuelling..YES)

(NON HEATED fuel mist is WHITE)

Forget the EGR. Even if it was blocked you wouldn't notice any problems since it would be no different to if it wasn't fitted at all, or if it was blanked off. You'll only get an error from the car if the ECU thinks the EGR is not opening or closing when it should be. No EGR (blanked, blocked or removed etc.) actually makes the car run marginally better, since there's more oxygen in the mixture and less CO/CO2.

White smoke out of the back and hesitation when cold is mostly pointing to the head gasket.

If you're getting coolant seeping into the combustion chamber overnight then it will effectively be weakening the mixure - interfering with the combustion process - when you start the car. It gets better when it's hot because the coolant seep is probably minor and once you've burnt it off, there's just less getting in there... and in any case, in a warm engine a slightly weak mixture burns more easily.

Check the coolant level to "prove" it or not. If it looks low, give the beast a compression or a "sniff" test. If you can, bleed the radiatore and see whether there's any gas in it. If your coolant reservoir is full of bright pink coolant, then that's a good sign. If you're thinking "but I only ever put water into that brown goo.." then that's less good.

If your gasket is okay, then I would look at fuelling; replace the Coors tin on the bulkhead and get your mate to bring round a fuel pressure reader for the fuel rail, if he has one.

The pump is supposed to get on the case and pump more fuel when you accelerate but if the pump is knackered or weak then you're effectively getting fuel starvation. If the pressure checks out okay then you're on a detective hunt for a duff injector or something... but that's one for later.

Ralf S.

Thanks for all the advice. Still waiting on my mechanic friend. I am not a mechanic so don't want to tackle anything myself.

Coolant seems ok. It never really loses any.

Yesterday when it was much warmer outside (almost 15 deg) the car ran smoother and did not hiccup with the power drop.


QU : Do the glow plug only activate to start the car and warm the cylinder or do they stay on for a period of time ? I do not have the glow plug fault warning lamp on the dash so never considered that it could be the issue.

At first I thought injector or fuel pump but the car is ok once up to temp so I kind of ruled these out.

The glow plug lights up when you turn the ignition on but then goes out. It heats the combustion chamber enough to ignite the diesel so once the engine is running it's no longer needed.

I'd still check out the fuel rail pressure.. the transition from cold to hot running is showing up *some* problem.

Also, how old is the lambda sensor? These have a heater to heat them up at low rpm and the heater turns off when the rpm increases. I don't know the diesel's change-over point.. but anyway, if there's hesitation as you pass a certain rpm (cold engine and also when it's warm, although maybe less noticeable) then it could be the lambda.


Ralf S.

Doesnt jtd have the afterglow function ? Where its glowing olugs after start to minimize the choke ?

Possibly.. and the thin walls of the plugs 'tube'

Should tetain heat..

But.. it its not being elecyrically heated.. it will temain a COLD cylinder for several minutes.

flyingdutch said:

Doesnt jtd have the afterglow function ? Where its glowing olugs after start to minimize the choke ?

Click to expand...

Yes.. the initial "glow" occurs between 2 and 5 seconds.. then the plug switches to the afterglow phase, which lasts 3 minutes or until the coolant temperature reaches 70C, whichever is the soonest. You won't get the afterglow if the coolant is already above 70C but you do always get the initial glow.

I suppose a duff thermostat will tend to kill the glow-plug... as would using a glow-plug not designed for after-glow on any engine that has an after-glow function.

The other random bit of nerdiness to remember is that a diesel will heat up anything (including air) as it compresses it. It's the compression/temperature boost that makes the biggest difference to combustion. The only "tricksy" is that the cold air coming into the chamber will cool the glow-plug momentarily, so a plug has to be designed to have enough latent heat in it to stabilise this "draught" cooling.


Ralf S.

Well the part of diesel heating up the air would be correct if we were talking about old indirect injection diesels which can basically coldstart without preheating, as for the newer engines that is comonrail design this is not entirely true . Newer engines run on cr 21 and below so it doesnt heat up that much any more . As for the problem had few JTD's with messed up ambient temperature sensor in MAF which randomly on cold showed -240°C so worth checking out also injection correction should be checked mechanically and electronically.
And sorry for terrible english:/