Calling all mechanics

[Prototype_No.98]

Iv been having a mysterious problem with my car that so far, many different mechanics have been unable to diagnose what is wrong with it and even myself nor my colleges (who all work in a Diesel Engine Company) are unable to find anything. So im wondering if anyone here might have any information...

Il try to give as much info as simple as possible...

Engine:
2.4L, 5 Cylinder Diesel.

Problem:
- Car idle is unbalanced/rough on startup, with white smoke (oily smell).
- Sometimes the car will die as soon as the engine fires.
- Sometimes the car will take a while for the cylinders to fire/turn over.

Condition:
- When the engine is cold (Thermostat reeds 0), or not been running anytime around/after 4 hours.

Side Problems:
- Car will occasionally cough or splutter (Only noticed while in motion).
- Sometimes reduction of power for a few seconds (Only noticed while in motion).

Notes:
- White smoke clears after revving the engine.
- Rough/Unbalanced Idle clears after revving the engine.
- Adding a high concentration of Fuel Additive for the past few weeks has only reduced the problem slightly.

Tests Done:
- ODB Reports no faults.
- Electrical test on glow-plugs report all glow-plugs are normal.
- Electrical test on Wiring loom/connection to glow-plugs reads normal.
- Diesel return flow test has all 5 bottles filling at the same rate.

To me it sounds like an Injector or injectors may be leaking when the engine is off.

Any help would be greatly appreciated.

-=EDIT=-
Additional Facts:
- Not Loosing any coolant or Oil.
- EGR Valve has been replaced to no effect.
- Mass airflow sensor has been cleaned.

[Sabot02]

I'm far from mechanically minded and I haven't a clue about the Thermostat, but I do wonder if there might be oil leaking into the engine where it shouldn't be. Maybe too much oil has been put in. I dunno, but I've heard it can cause similar problems in diesels. Just a guess.

[Compston]

If you notice a distinct loss in speed/performance it'll be the injectors. The kind of problem though would need to be determined by sight.
If there's no loss in performance i would check to see if it was mistakenly given petrol instead of diesel.

[Prototype_No.98]

I'm far from mechanically minded and I haven't a clue about the Thermostat, but I do wonder if there might be oil leaking into the engine where it shouldn't be. Maybe too much oil has been put in. I dunno, but I've heard it can cause similar problems in diesels. Just a guess.

Oil would come out the exhaust as a blue tint.
Odourless white smoke is a sign of a coolant leak or water in the engine, however if there is an oily odour it is most likely unburnt fuel.
Burnt fuel is normally Black.

Iv kept an eye on the Oil and Coolant levels and its not losing any fluids.

[Prototype_No.98]

If you notice a distinct loss in speed/performance it'll be the injectors. The kind of problem though would need to be determined by sight.
If there's no loss in performance i would check to see if it was mistakenly given petrol instead of diesel.

Its not a great loss in power, it feels like the throttle is lifting off when my foot hasnt moved at all, which only lasts for a few seconds.
Both the power loss and coughing happen very rarely, but it is noticable.

[Husker]

Get the high pressure fuel pump checked and also the inlet manifold could need cleaning. Not a little clean with some solvent sprayed in, a good clean with it off the car. Also get the EGR valve cleaned or removed, you can add a blanking plate but that will require an ECU remap. Also once the manifold is cleaned and you're 100% sure the EGR is fine, i would recommend getting an oil change. Regardless of what the dipstick says, only put in the amount that is listed for that car.

Tbh i can't remember what we've already discussed but i did do some searching on this and it seems people are having problems with the Alfa diesel engines and their problems seem to match yours. They all recommend the manifold and EGR clean. Apparently the engine has swirl butterflies and they fail when coked up causing these problems.

You can get a pressurized inlet clean, it's expensive (about £180+) but worth it. That'll make the inlet like new again.

[Prototype_No.98]

I never thought of the Inlet manifold, I didnt think it was an issue given my cars low mileage.
I could take it apart and see if it needs a clean out.

I really wish I could blank off my EGR Valve.

[cmdraftbrn]

if its fuel injected. the rails could be dirty causing the injectors to stick.

[skitxx]

Does sound like the injectors. That white smoke is excess fuel hitting the exhaust and burning up. Since it happens just at start up it sounds like they are leaking a lil bit. If it was a serious leak you wouldn't be able to start your vehicle due to hydrostatic lock (too much fuel in the cylinder to where you couldn't get the compression needed to fire). In the marines for our smoke screen on our vehicles it was a nozzle that would spit fuel on the turbo and it would create the white smoke.

[Prototype_No.98]

Iv been thinking of disconnecting the electrical connections from each injector to see which injector is causing the smoke.

Such as this video.

However my car creates a lot of smoke so it could be more than one injector at fault.