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Excessively smokey Td5


GBMUD
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My 90 Td5 has done 140k miles, I have owned it for almost 10k miles and it has always made a lot of black smoke. It does not smoke excessively all the time, not even under full throttle/boost, just some of the time - generally at the lower end of the rev-range, but well above idle and when on boost. I have not been able to establish any real pattern to it, though I would say it is not just random. It seems OK when cold, and much better when very hot - after a long/fast run - but when pottering about, a few minutes after startup and continually thereafter, it seems pretty consistently bad. Higher RPMs and gentle on the throttle it is OK, but sometimes even being gentle with the throttle it will get smokey. On the motorway I can set the cruise at 60 and there is no sign of smoke.

This is a black smoke problem, not blue nor white.

I have had the car chipped - though it is pretty much no different now to how it was when I bought it.

There is a new OEM MAF sensor fitted, the MAF sensor was US when I bought it.

Engine seems OK otherwise - sometimes I feel the turbo is lazy getting wound up/a lack of power in the bottom end. Little/no oil use, no coolant loss. I have cleaned and then disconnected the EGR valve - it appeared to be sealing well.

Who can suggest where to start? I am assuming I should be looking at sensors, but which one first? I have access to a Rovercom, but no faults recorded.

Chris

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Black smoke is un-burnt diesel.....

This could be less air than required at the time it smokes or more fuel than required...

I would start with the real basics...

Remove air filter and see if it runs any different.

Check the turbo waste gate is moving ok...

Temporarily blank the EGR to eliminate it?

Borrow MAP sensor out of another TD5....

I get a cloud of black smoke when I pull away and have the throttle down. (Usually worse when slightly bogged down when trying to move off.)

Rarely any thing noticeable under other conditions unless I bury the throttle at low RPM and over-fuel when I get black smoke bellowing out the back..... :)

I have a spare turbo if you want to go that far trying other parts....

Neil

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The wastegate on TD5s can get sticky - the spindle where the pressure-actuator rod goes into the turbo housing clags-up, meaning it can stick closed or open depending on how it feels.

If it sticks open you get truly-lethargic performance. If it sticks-closed you get loads of performance until the ECU senses overboost and then switches to 'limp-home' performance - which goes away if you shut-down and then restart the engine.

You say it smokes at the 'lower-end' of the rev-range; If that means under-2000RPM I'd suggest perhaps go for a lower gear? TD5s are 'modern generation' diesels and love to rev - they tend to clatter smoke and struggle a bit if you're using lots of throttle at low RPM.

"If in doubt, change down" - the electronics mean you can't over-rev a TD5 - my 90TD5 will do 70 in 3rd when chasing BMWs.

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It smokes where my last Td5 did not. I do not have a tacho, but I would guess that it smokes through the 2000rpm point. I am inclined to choose a tall gear, but however I drive it is pretty much the same.

Wastegate is OK, I checked that.

I wonder if I can get someone to drive behind me while recording real time on the Faultmate and then compare the sensor date to the video...

Chris

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I wonder if I can get someone to drive behind me while recording real time on the Faultmate and then compare the sensor date to the video...

Chris

Where are you in Sussex? Could possibly help if you have a suitable dash cam.

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So, what have I found out?

Yesterday I cleaned the MAP sensor and the AAP sensor. Neither was specially dirty, but once they were out... I also made an EGR blanking disk, just to eliminate EGR leakage as a potential factor. On the test drive it did seem less smokey - but it was so wet and windy that I could not make a real assessment. A little later in the day I concluded that is was still smoking just as badly.

Today I have remapped the ECU which seems to have made it a lot better. The only maps I have access to are named by number only, with no further details, so I have just chosen a different map and flashed it on. It now seems much less smokey, but still has better performance than standard. Some of this reduction in smoke may be down to the throttle mapping apparently being different - one needs more throttle to get the same power, though 0 and 100% are still the same, it seems more linear than before. The last map seemed to give 75% performance for 20% throttle movement. In any event, it appears a lot less smokey so I will run it round like this for a few weeks and see how I get on.

Thanks for the advice and ideas...

Chris

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