White smoke at start up?

During the recent colder weather (but still above freezing) my TDI has been producing quite a lot of white smoke at start up. It last for a couple of hundred yards of driving an then disappears. It never used to do this. In every other way the car starts and drives normally and has no black smoke. It uses no coolant so it's not steam (has that diesely smell anyway). Could it be glow plugs? Maybe just one has gone bad, or do all TDIs do this on a cold morning? The warranty runs out in a month or so, so I'd like to sort out any such problem now.

------------------
1996 Passat Tdi estate (wagon (variant))
See my Peugeot / Passat site

Christi,

Given that you said the ambient temp is above freezing, it could be the glow plugs. But it could also be crappy fuel with a low Cetane value. Try buying a high Cetane fuel (45 or better) or add some Cetane inprover first to see if that helps. You can get Bardahl's Cetane improver at Walmart. If you car is still under warranty, it never hurts to let the dealer check it out anyway.

White smoke at startup in cold weather is normal for diesels. Truckers call it "cold smoke". My TDI will let out a tiny puff on the coldest day, but that is about all. I use 47 Cetane Amoco PowerBlend diesel with a shot of PowerService's Diesel Supplement.

Hope this helps.

Rich

------------------
Rich in Northern VA
2000 Jetta GLS TDI Manual
Canyon Red/Beige
w/Lux/Cold/6CD

The cetane rating of fuel here in the UK is pretty good anyway, and I use Millers Diesel Clean+, so that isn't the problem.
Could it be because I disabled the EGR?
Could it be water vapour in the exhaust?
My dealer told me that with a bad glowplug that the engine would not start and tickover so well. The engine starts instantly and is very smooth.

------------------
1996 Passat Tdi estate (wagon (variant))
See my Peugeot / Passat site

Sorry,

I didn't even look to notice that you are in the UK.

Rich

If your still under warranty, have the dealer check your glow plugs, injectors, injection timing, ect... Have they go right down the line and conduct a search and destroy mission. Honestly, the white smoke is probably normal, my A4 will emit a small puff of white smoke upon ignition if the outdoor temp is below freezing.

[This message has been edited by Strack (edited January 25, 2000).]

White smoke on startup is simply unburned fuel molecules atomized in the air, they go away simply because they are burned as the engine reaches proper compression combustion chamber temperatures. If it is excessive, the glow plugs could be bad (either one or more) however that would trip a bright check engine light on the dash. If that is not the case, it simply is normal procedure for your TDI. Cetane boost will decrease this occurrence and will good fuel supply, bad fuel will make it worse. The smell of white smoke is also rather raw as it constists primarily of incomplete combustion products which cannot be oxidized by the catalytic convertor since it too is not up to operational temperatures either at initial start up. The smells are the various aldehydes and ketones that result from incomplete combustion of middle distillates, they are VERY CHARACTERISTIC to the human olfactory sense (THE NOSE!!!!).
Good luck Christi, perhaps moving to Bermuda would cure the problem?heheh

Some white smoke is very normal when it gets cold as has been noted above, and disappears as soon as it warms up enough to burn all of the fuel. It is composed of atomized fuel components that were not burned in the cylinder and will present a very strong smell.

As long as it disappears quickly, you should have no trouble. I get a little in the morning, but it usually disappears before I get everything situated and pull out of the driveway.

I am assuming this only happens on a cold start, and not on a start after a shutdown and then restart shortly after while the engine is still warm. If this is the case, then you're fine.

If it did not happen last year (have you had the car that long?) then maybe you should have everything checked while still under warranty. That would be a smart move.

------------------
Always interested in steep & deep

OK, let's run through this logically (hope you guys don't mind listening to my ramblings):-
Injection timing: Retarded timing causes white smoke, but why should that suddenly change?
Glowplugs: Got no warning light (does the Euro one warn you a glow plug has blown?), got smooth idle. Maybe I should check them, but I suspect that they're OK.
Worn injectors: Can a worn injector give you white smoke when cold, but not black smoke? The black smoke output is very low, recently had it government tested.
EGR: In European models, there is no warning light if one disconnects the EGR, but is it possible that the computer detects it and retards the timing to compensate for lack of?
In fact even when warm, if I leave the car idling and walk round the back, I can smell the emissions, even if I can't see them. I shouldn't be able to smell anything, should I.
BTW I don't have a VW or dealer warranty, I have one from an insurance company, and it doesn't cover everything. I will have to pay for any checks that I can't do myself.

------------------
1996 Passat Tdi estate (wagon (variant))
See my Peugeot / Passat site

christi: That's perfectly normal diesel engine behavior. It has nothing to do with injection timing, though more advanced timing might help the problem. (The ECU probably advances the timing when the engine is cold anyway, but I'm not sure.) A cold diesel engine, even with the glow plugs operating, cannot completely burn the fuel. The white/blue smoke you see is a fine mist of unburned and partially burned diesel fuel. The colder the temperature, the more white smoke is produces and the longer it continues. Big commercial diesels belch out HUGE clouds of white smoke when they're started in cold weather, and they continue to do so for several minutes. It takes a long time to heat up that much metal! But don't worry about it. Your car is fine.

-mickey

During the fall months, when the temp varied a few degrees above or below freezing, there was a fair amount of white smoke upon startup. To my amazement, now that the temp is always many many degrees below freezing, in the Ottawa area, there is no smoke that I can see. I hope that doesnt mean anything bad, like being too lean or something. Mileage has dropped to around 50mpg cdn during the past week or so with the temp being around -15 to -20c.

My mind has been boggled at how LITTLE white smoke my TDI makes, even starting after an overnight soak at +10 degrees F. Just a puff, and then nothing. It stops way, way before the engine could even begin to warm up.

I've been using a good quality cetane boost though.

Well I re-connected the EGR last night, and this morning viola, no smoke, but then it wasn't very cold this morning. Also I had a look at the warranty paperwork and it says quite clearly that it doesn't cover either diesel injectors or glowplugs. I'll let you guys know what happens next time we have a cold morning.

------------------
1996 Passat Tdi estate (wagon (variant))
See my Peugeot / Passat site

Black smoke = high fuel/air ratio

Blue smoke = oil in exhaust

White smoke = water/moisture in exhaust

"unburned fuel molecules atomized in the air" is pure B.S..

------------------
Ric Woodruff

Braumeister von Sehr Guter Bier
Since the Last Millenium

Ric, please just shut up if you don't know what you're talking about. It's obviously raw fuel. We all know it. Where is this vaunted "diesel experience" you keep talking about?

-mickey

Where there is smoke, soot, drips, and other undesirable TDI excretions, there will be Ric, his ride has excretes 'em all.

The problem is the description of the smoke.

Pure white "smoke" is probably steam and signifies a bad head gasket or other problem.

Bluish smoke signifies oil burning.

Dirty white (I call it black, but its not really black more grey) smoke is normal on a diesel when its cold.

Smoke from a diesel isn't necessarily a bad thing. People are trained that when they "see" smoke coming from a car its bad. Not necessarily true with a diesel however.

I would describe it as more of a gun-metal gray in some lights, and more white in other lights. Even appears blue sometimes. One thing's for sure: It ain't water!

-mickey

Sorry Ric, we know different.

Christi,
Recently had similar white smoke when starting, intermittant black smoke when accelerating hard, my fuel milage had decreased from average 43mpg in town to oscillating 34-42mpg over 5 or 6 fill ups. I had the injector pump timing checked and it required adjustment. Unfortunately the service manager could not tell me the relative point it was at or the amount of adjustment neccesary to bring it back into spec. I picked the car up on Saturday and the tech whom had performed the work was off. Noticible improvement in acceleration in 5th at lower RPM's, no longer any smoke. I have not had it back long enough to correlate milage, and no explanation as to the shift in timing.

------------------
72 412,
72,77,82,85 campers
68 bug, 89 and 91 foxes
71, and 72 914's
98 jetta TDI

Ric,

Everyone is talking about the small amount of white smoke produced on startup when it is cold outside. The temperatures you experience there in Florida do not count.

If it is merely water, why does it smell so bad? Water vapor dissipates in seconds. This stuff hangs around. There are very large differences in appearance, behavior, and smell between water vapor condensing from exhaust (normal combustion), coolant in fuel (abnormal problem), and cold diesel white smoke on startup.

Please don't confuse others; you might panic someone who is inexperienced, and you reveal your own ignorance. It is unbecoming.

------------------
Always interested in steep & deep

Well I'm not so sure this morning. There was frost on the car, so it must have been below freezing. I started the car and went and had a look around the back, "hurray" I thought "no smoke, wonder why reconnecting the EGR has done that..". I then drove down the drive and onto the street. About 70 or 80 yards later I decided that I couldn't really see safely to drive on the main road, so got out to scrape some ice of the window, there was white smoke !!! Wierd.
If I had some kind of injection, glow plugs, timing thing I would have seen white / grey / blue smoke straight away, as soon as the engine started, as soon as those diesel molecules hit those cold cylinder walls, yes? It would have come out faster than I could have walked around the back, yes?
So I'm coming to the conclusion that it is just water vapour.
It's definitely not head gasket. This car hasn't used a drop of coolant in 12000 miles.
Why does my TDI blow water vapour out the back when no other diesel I owned did it?
Why do petrol engines blow out water vapour and diesels don't?
I need to understand.
Ric, have you actually seen water vapour coming out of the tail pipe of your TDI with your own eyes? or are you talking theoretically?

------------------
1996 Passat Tdi estate (wagon (variant))
See my Peugeot / Passat site

hmmmm. Just the TDI, no previous diesel... Could it be because the TDI has a catalytic converter? One of the by-products of a catalytic converter is...water, which, after the catalytic converter gets hot enough to actually function, comes out in the form of vapor, (or maybe as vapour in the U.K.).
Of course, this is just speculation on my part; I have not gone out to observe my Golf TDI's exhaust.

I'm thinking that the TDI produces as much smoke as any previous diesel except that it is so clean as opposed to previous diesel VWs that the smoke is almost scrubbed as compared to previous diesels I owned.

My 80 Dasher (Passat) put out as much black/brown colored smoke as needed to cause a scene in public. But maybe if you removed a lot of particuates and other pollutants, also made the engine a lot more efficient, then maybe all you'd have left is this almost white smoke with a hint of diesel floral bouquet???

[This message has been edited by JeffT (edited January 27, 2000).]

JeffT, the TDI doesn't produce smoke anywhere like previous diesel engines, read some BOSCH SAE papers about the legistlated soot and smoke limts in Europe and how VW-AUDI programmed the entire smoke map parameters into the EPROMS of the TDI ECU.
Basically, there is absolutely no comparison, one of the true technological achievements making the TDI such a marvelous engine.

JeffT is right on the money. The ONLY way you could be dumping raw fuel out the tailpipe is if the compression of one (or more) cylinder(s) is so low that no fuel ignition is taking place, which is extremely unlikely. It would be painfully clear to you that you have a major engine malfunction i.e. a bad cylinder.

If your engine is running, ALL YOUR CYLINDERS ARE FIRING and burning up the fuel, therefore not dumping raw fuel out the tailpipe.

Either diesel fuel ignites in a cylinder, or it doesn't. It can't "partially" ignite and put partially raw fuel out the exhaust.

Analogy: Lite a firecracker fuse. Either it will explode or it won't. No in between.

------------------
Ric Woodruff

Braumeister von Sehr Guter Bier
Since the Last Millenium

Yeah, yeah, yeah, but why does the TDI produce water vapour, when none of more other diesels did?
Why do petrol engines produce water vapour? there isn't any water in petrol is there?

------------------
1996 Passat Tdi estate (wagon (variant))
See my Peugeot / Passat site

ric, if you can't use your mind, at least use your nose, it is more powerful.

HELLO, CAN ANYONE HEAR ME?
Why should a TDI produce water vapour when "normal" diesels don't? is it the cat?
Why do petrol cars produce water vapour?

BTW Ric, if you retard the timing say 2 degrees of your diesel, any diesel, you will see a shed load of white / grey smoke. When the engine warms up a bit it will probably clear. Also if you take on old style diesel, like a rabbit, disconnect the glowplugs and crank that sucker (cold) till it starts (about 30 seconds to a minute) you will see a shed load of white / grey smoke too. No firecrackers. I've personally done and experienced both of the above.

[This message has been edited by christi (edited January 27, 2000).]

Christi,
water is a product of all kinds of combustion with hydrocarbon fuels. Even burning a candle produces water vapor. The two main by products of combustion are water and carbon dioxide. There is all kinds of other stuff too in the emission stream, but water is a large component.

Gasoline engines produce water as well as diesel. This is pretty obvious where I live. When it is really cold, little white clouds follow all cars around as the water condenses as it exits the tailpipe and hits the really cold air. Really big plumes of water vapor are evident at power plants and boilers for large buildings.

However, the water vapor will not have any hint of blue or gray color.

How come my old Peugeot diesel definitely did not produce water vapour (I had it for 8 years, I would have noticed) and the TDI does, apparantly?