The color of smoke emitted from the tailpipe of a modern TDI diesel engine can denote specific indications of problems or lack thereof.
during a cold start is usually indicative of a little condensation / moister in the engine or exhaust system. In most cases this is somewhat "normal
" according to VW, even though most of it can be corrected with a good additive and cetane booster.
usually indicates oil that gets into the combustion chamber and is burned (for one reason or another). It is also considered "normal
" for a diesel engine to burn a little
bit of oil, including the TDI with tighter piston to cylinder bore clearances, which naturally reduces the amount of oil consumption.
indicates too much fuel or too little of air within the combustion process. This could also result from poor injection timing as well or from a Forum member rapidly stepping on the accelerator pedal to give a tailgator a "smokey!"
at all indicates that you are probably
doing many things right and should stay with your outlined maintenance plan that appears to be working. Furthermore, the quality of diesel fuel plays a large role in the color of smoke or lack thereof during a cold-start.
Now back to "white smoke,"
which also can occur when there is not enough heat
to burn the fuel. The unburned fuel particles go out the tailpipe and typically produce a rich fuel smell. It's not unusual to see white smoke in the exhaust during cold weather until the engine warms up.
Moreover, with very littly heat and white smoke, bad glow plugs or a faulty glow plug control module can cause somewhat excessive white smoke on engine start up. Low engine cranking speed may also produce white smoke on occasion too.
If white smoke
is still visible after the engine has warmed up, the engine may have one or more bad injectors, retarded injection timing, a worn injection pump, or coolant is somehow getting into the combustion chamber. Low compression producess less heat than normal and can also be a source of white smoke. And finally, according to my local Bosch Injection Center, air in the fuel system can cause extra white smoke as well.
In conclusion, a puff or two of white smoke during a coldstart is normal. Very little or no smoke is rare and confirms your engine is close to performing at peak efficiency. Blue or black smoke can
be warning signs of inefficiency or a TDI'er moving with a purpose! [img]images/icons/tongue.gif[/img]
[ December 20, 2001: Message edited by: Turbo Steve ]</p>