Smokey Hdi Xantia

rmunns · Unread post by **rmunns** » 12 Aug 2009, 08:02

Hdi90 (Sept 2000; 39,000miles) shows black smoke on hard acceleration. Particularly noticeable last night going uphill with car headlights behind. Stain appears on (silver) bodywork around exhaust, but this takes a long time to appear (eg. after a trip Doncater - Bordeaux there was a light film of black).

Car has been ruthlessly serviced by main dealer since new.

Is this a big problem? Car passed it's MoT in April 09 (UK) and June 09 (here in France).

marsalek · Unread post by **marsalek** » 12 Aug 2009, 09:20

Hi, even the HDis smoke on hard acceleration

And with car headlights behind it is particulary noticable. So this is perfectly normal and no point to worry about.

For a comparison, have a look at some VW TDi (PD) accelerating. Even at daylight you notice clouds of smoke. So don't worry.

Karel

JamesQB · Unread post by **JamesQB** » 12 Aug 2009, 18:36

Out of interest, what are the usual causes of black smoke upon acceleration? I gather it's too much fuel, and think I recall various culprits like air filter being clogged, etc. Any others?

red_dwarfers · Unread post by **red_dwarfers** » 12 Aug 2009, 19:27

Carbon deposits are another one which require an Italian tuneup 8)

marsalek · Unread post by **marsalek** » 12 Aug 2009, 21:48

JamesQB wrote:Out of interest, what are the usual causes of black smoke upon acceleration? I gather it's too much fuel, and think I recall various culprits like air filter being clogged, etc. Any others?

Usually, as Kev noted, carbon deposits. Clogged air filter causes less air intake, what is compensated by the air flowmeter data sent to the engine ECU - so you notice just less power but no smoke. But with faulty EGR valve you might get clouds of black smoke due to unburnt diesel.

Karel

rmunns · Unread post by **rmunns** » 13 Nov 2009, 16:39

Updating;

injector cleaner (Tesco, £3.99) sorted it out.

Unread post by **Old-Guy** » 13 Nov 2009, 17:28

I left Heathrow on Wednesday afternnon just in time to join the 'rush' (70 max) westwards on the M4. When I finally turned off at J18 and clogged it up the A46, I saw noticeable smoke in the headlights behind for the first time ever.

My Montego Diesels would do this in a big way - vehicles behind would vanish in the 'puff' of black smoke!

Under gently motorway cruising, the turbo is spinning gently and doesn't get really hot. After quite some time, the turbine (and various other places) accumulate a layer of soft soot. Then the first time you really clog it, the blast of red-hot exhaust gas dislodges most of it but there's too little oxygen to burn it all so a cloud of soot particles pours out of the tail-pipe.

It helps to buy quality fuel instead of supermarket muck - even the dirty old Montego was a lot less smokey on Shell or BP.

Unread post by **lolingram** » 17 Nov 2009, 17:23

It helps to buy quality fuel instead of supermarket muck - even the dirty old Montego was a lot less smokey on Shell or BP.

This is wishful thinking IMHO...

Unread post by **Old-Guy** » 17 Nov 2009, 17:57

"Supermarket muck" was perhaps a bit strong but the fact remains that the primary consideration for supermarket fuel is lowest possible price for fuel that meets the minimum specification.

The specification will omit any additives not absolutely essential to meet the standard. In contrast, 'quality' fuel like Shell or BP contains detergent additives to help keep the fuel system free of sticky residues.

I proved this point with my elderly father-in-law's Escort: a recurrent problem of a gummed up throttle body was cured by always filling up at our local Shell station instead of T***o in the mistaken belief that the later 'must' be cheaper. In fact our local Shell station does such a huge trade that it prices are very competitive - one reason why it has such a huge turnover.

Unread post by **lolingram** » 17 Nov 2009, 18:27

"Supermarket muck" was perhaps a bit strong but the fact remains that the primary consideration for *supermarket fuel is lowest possible price for fuel that meets the minimum specification.

Cleaner than *some of that stuff the Veggy boys use I'll warrant. I agree 100% about the Montego Perkins Oiler... horrid bit of kit.