Euro 4 D5 rough running smoke AFTER running a few minutes

[Cossie7]

Afternoon all,

Bit of a strange one here

Cars had loads of work

First thought it was injectors so had a swap about and no change. Compression test, injector quantity etc all OK.

Car starts fine from cold but after a few minutes it's like flicking a switch and the car starts running rough and smoking quite bad

Turning the car off and re starting and it does the same thing again

Car has egr blanked and dpf is gone as though this is what the issue was as oil level was rising and smelled of diesel.

Also don't know if it's coincidence but has a decent oil leak at the rear of the engine near the timing belt which seems to run down to the lower engine mount.

From reading a couple other threads there seems to be some discussion on a blocked oil separator and maybe a vacuum leak to the egr bypass valve?

It feels like an electronic fault as like I say it runs great then it's like something turning off or on and it instantly starts running rough and smoking....

Pretty much the opposite of normal running faults which are from cold then disappear after a few minutes...

If anyone has any ideas I'd be greatful.

Many thanks

Cossie7

Sorry originally posted in the V50 section but due to it been a D5 I think it's probably better suited here.

[StaffsS60]

Coming from the world of VAG it could be a temperature sensor issue- Mk2 drivers will be very familiar with blue sensor issues.
Have you noticed a slump in your fuel economy? Could be that the ECU is registering a permanently cold engine state and over-fuelling/ running too rich.

[Cossie7]

Hi, thanks for the reply, looking at live data there is nothing out the ordinary...

I'll have to have another look as now you've said it I can't remember if there is coolant temp and cylinder head coolant temp readings...

Mind you thinking about it, if I turn it on and off after times it will sometimes behave and if it does behave and gets hot it will drive fine and not do it until its been left for a while.

I know where your coming from though had a few cars that were undriveable when the cts was acting itself.

Cheers

[Cossie7]

https://youtu.be/Vf_gyJiYJWo

Video 1 - MAF acting squirrely ?

[Cossie7]

https://youtu.be/U8SKTeeJtiw

Video 2- car running fine then you hear it change and seems to drop a cylinder and roll smoke screen

[StaffsS60]

MAF could be a good shout, is there any change in the data when the noise varies?

[Cossie7]

No mate, not with the live data side of things.

I've been unsure about the MAF for a while but cleaned it and thought it was OK. First time I've noticed it going to -75°c on ignition though....

Seems to sort itself out when running but pretty sure it shouldn't do that.

Only thing that goes way off when running bad is the fuel in jector check readings. All 5 go to +/- 4 or 5.

On good running cylinder 4 shows 2-3 but I've tried 3 injectors in here so either I'm really unlucky and all 3 are boned or something dickie.

Oh I've replaced all the injector plugs aswell.

I've ordered a set of high pressure pipes so I can cut one up and make a blanking plug to blank cylinder by cylinder to try and isolate it.

Think I might be edging down the garden path a bit though doing that as like I say its totally fine from cold start then all of a sudden "click" and runs like a bag of poo.

Cheers

[StaffsS60]

Good luck with the fix matey, I wouldn't overlook that MAF though

[hentsy]

Hi. Did you solve your problem? I have exact same thing with the same engine. Injectors are good, tried from another car. Massive unburnt diesel smoke, and it’s gone after a good drive, when engine is hot. Have also EGR, DPF, FLAPS off.
Other than that, car runs and drives perfectly, low fuel consumption.