Suggestions for a 4.0 TDI smoking?

Artermis · #1 27th June 2016, 04:43 AM

Kind of dreading posting this - knowing what it's like if you go looking you're likely to find things, so I really don't want to have to admit I need to look into this....

A friend and I were out for a drive at the weekend, he was following me for a while. Eventually he pulled me over and said "you realise how much that smokes, sometimes I can barely read your number plate"

Personally I'd never seen it, but then I look forward not back. he suggested it wasn't whilst accelerating hard put on mid/partial throttle.

The friend in question is a truck mechanic by trade, so he isn't completely clueless about such topics so I tend to take his words fairly seriously.

We swapped cars for the couple of miles remaining and honestly I can't say I picked up on anything although we were sat in traffic mostly.

Is there anything know or worth checking to see if there is actually an issue?

I had checked for fault codes a month or so ago when coding up some new bits and although there was a lot of codes that seemed flat battery related nothing stood out to me.

I've always thought it felt a little gutless at high revs, which the box likes to do on kick down annoyingly, but I put that down to it being a diesel - it has good low down torque which I'd expect.

Is there any boost pipes or anything known for leaking? Are MAFs an issue? Do EGRs tend to be a problem? Do people block the EGRs? I've blocked on previous cars with good results.

I don't have any undue or scary noises, can't say fuel consumption is an issue, running temps are spot on, doesn't eat oil or anything like that.

Thanks folks, appreciate I might be scratching around in the dark for a problem that possibly isn't there!

snapdragon · #2 27th June 2016, 08:03 AM

The injectors from that era leak and so when idling, unburned fuel builds up and then gets evapourated when accelerating. This is usually in stop start traffic though. Very common story on the 3.0 TDI as they are 10x more common but the injector is the same part to all intents and purposes.

Burnzybubbles · #3 27th June 2016, 07:37 PM

What colour? Would help determine what could be wrong with it, leaky injectors is usually white smoke, has it had a full service and filters replaced? Have you checked the condition of the egr valve and inlet system?

Artermis · #4 28th June 2016, 05:36 AM

Sorry guys - black smoke, not white.

I've not checked EGR setup, no. I'm not familiar with the EGR setup on these motors so I don't rightly know what to look for. Any diagrams or pointers?

Joe2.0E · #5 28th June 2016, 11:31 AM

Black Smoke could indicate issues with the Turbo but if its passing an MOT and mpg is okay, I would ignore it unless you want to throw money at it.
Has it got big mileage ?

Artermis · #6 28th June 2016, 06:06 PM

Nah it's only on 125k, not a lot really.

I'm tempted to get it on a ramp at weekend and check for boost leaks (i.e. loss of charged air making it go rich) and blank the EGRs off to see if that makes a difference. I must have a bit of cake tin or something somewhere to make a couple of blanks up with; unless they're visibly caked up and not functioning properly in which case I'll clean and restore.

I just don't know if it will throw a metered air or air quality code up; later cars I know certainly will but I don't think cars this early should care - if memory serves it's only about euro 4 on that it got clamped down on.