406 HDi 110 Power Loss/Black Smoke

[davei]

Hi everyone. Hope someone out there can help?
I have a high mileage 1999 estate with a worrying problem. The car runs fine from cold and gives good fuel consumption.
However, if you get stuck in a traffic jam for more than about 20 minutes, the trouble starts. The engine idle speed is ok but when you go to move off there is a huge loss of power and thick black smoke embarrassingly follows you down the road!
If you have a clear road in front of you and with careful use of the throttle the engine will eventually clear and return to normal after 5-10 miles. The same problems occur if you go for a drive then leave the car in a car park and return after about an hour. The water temp is steady at about 80.
The injectors were reconditioned last January.
Help!

davei

[londoner1]

EGR valve???

[davei]

I'll have a look at the EGR valve. I know that some people isolate the EGR system by some means. Further investigation is needed on my part!

[Welly]

I would have a good look at the intercooler hoses and the intercooler itself (assuming it's a 110 model). You are not getting enough air into the engine for some reason so it's smoking - it could be leaking air from a hose somewhere, or a hole in the IC (look for signs of oil leakage here).

Other things would be Vac pump, air flow meter, egr, throttle position sensor, might be a case of trial and error if your engine light's not on

[davei]

Thanks for the replies. There is provision for 3 vacuum servos but only 2 are fitted. I took off the tube going downwards from the right hand servo but the performance went down so I put it back. I then took off the tube from the other servo and the performance seemed to improve, although it could have been my imagination!
I really need to let the engine tick over for 30 minutes or let it get hot and then let it sit for 45-60 minutes to try and recreate the conditiond that led to all the loss of power/smoke.
I will check the intercooler pipes over the weekend.
I fitted a new throttle position sensor last year. I have done some checks on the air flow meter but I will re-check.
There should be a photo somewhere although I am not sure if I have done it properly?

[mbell666]

Your missing the third one. judging by the lose hose its the one that controls the egr valve. may be something to do with the smoke/powerloss

[Welly]

The one on the right is for the turbo wastegate, the left one is the EGR, the "missing" one is only fitted to later models with an air dozer.

The strange thing is the two in the picture seem to have moved along to the right by one place maybe someone's been there before?

[Longintooth]

Hi
Initially the loss of EGR function will not affect the power since inducing exhaust gas actually reduces power and it is unlikely to create black smoke. EGR is admitted when idlling and at other low load points in the power range. It may fail the MOT if not working but may be borderline.
If you have smoke it is more likely to be injectors - I note you have had then done but that does not mean they are working good. One of the reason for black smoke is the injectors are not atomizing the fuel as they should, this can also be attributed to low injection pressure. The pump shuts off one of the three plungers in the pump at idle and should reactivate immediately the throttle is pressed. If it is not doing so you get a sloppy atomization through low pressure. Check it out. Other possibilities could be low turbo pressure but if it is occurring from idle it's doubtful since the turbo won't have chance to spool up anyhow at low revs.

[davei]

Many thanks for everyone's replies.
I think you could be right about the hp fuel pump. Perhaps one of the three pistons is worn and gets stuck and doesn't operate when it is required to do so? Can the pump be stripped or is it too specialist a job? A secondhand one may do the trick if I could get a good one. I might be able to borrow a Bosch diagnostic kit which will tell me the fuel pressures but the problem is trying to simulate the conditions when it all goes haywire. I will just have to let the engine idle until the problem starts.
Could the pressure control valve on the pump cause a problem and can this valve be tested ?

[Welly]

If you can diagnose-read the live data with the car idleing then the magic figure you're looking for is 298Bar at idle. This is the pressure in the common rail and should be rock solid and no less. A blip of the throttle will see 350, 400 etc etc.

[Longintooth]

Hi
I can't be sure of the pressures welly has given for the 406 but I think they are a bit out. A standard inline injector system operates at about 300bar but a common rail first generation is in the region of 1000 -2000 bar (yes bar not PSI) which is 29000psi. It should drop to around one third of of that on idle. The latest 3rd generation run at 2600 bar. However, for this purpose simply get hold of a gauge that can read this pressure and monitor it just to establish that the pressure flips back up to high with normal running you can worry about the exact pressure later. Caution - if you are doing it yourself make sure you work impecably clean
since if you get any muck in the system you can kiss goodbye to your pump and keep your fingers away from any pipes when it's running. The pump is easy to change and needs no timing but you may need to change the pipes with any replacement - they are supposed to be a once fit.

[Welly]

I can't be sure of the pressures welly has given for the 406 but I think they are a bit out

I was remembering the figure which all the diagnostic guys look for when they do live testing. And indeed I saw 298 Bar on mine and when revved it went to 400 odd.

[Longintooth]

Hi
Whilst it is proper to check the easy stuff first I still suspect the injectors as being the problem. From the description so much smoke from just setting off tells me there is an accumulation of unburnt fuel on each power stroke which points to the injectors not atomising - maybe a couple of holes bunged up on some nozzles. If it were mine I'd get them out and test them first off. Could be the fuel system needs a good clean out and filters changed. Diesels will go on forever
if they are kept clean and clear.