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Duramax Second Generation: 2004.5-2005 (LLY) Discuss the second generation (2004.5-2005 LLY) of the 6.6L Duramax diesel engine & associated components. 2006 LLY engine discussion belongs in Third Generation forum due to the differences of the 2006 LLY and the 2004.5-2005 LLY. Engine related discussion ONLY. is the premier Duramax Diesel Forum on the internet. Registered Users do not see the above ads.
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Old 08-02-2019, 10:06 PM   #1 (permalink)
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Light smoke after driving???

Hello. Today after driving a half hour, when I went to back into a parking spot I noticed smoke coming from the exhaust in the side view mirror. When I parked, jumped out and looked to see what color it was it stopped. It didn’t look white when I saw the smoke in the mirror Initially. Has anyone experience this before ?



2005 Silverado 2500 HD CC/SB
4" Flow Pro exhaust (No Cat)
Cold air intake
S&B Turbo Mouth Piece
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Old 08-03-2019, 04:36 AM   #2 (permalink)
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Black Smoke

1) If at idle, use the scan tool to cut out one cylinder at a time and see if the smoke disappears.
2) Dirty air filter
3) Exhaust leaks or Boost leaks, you can usually hear a boost leak as a high pitched squeal under load.
4) EGR and or MAF problems or intake leaks after the MAF sensor.

White or Blue smoke at idle when cold

If the smoke clears in less than 1 minute, this would be normal depending on temperature and altitude. Blue white smoke that burns your eyes is un-burned fuel; cold temperatures, high altitude and excessive idle time all mean cold combustion and white smoke.

1) Possible bad injector, use the scan tool to cancel one cylinder at a time and see if the smoke clears up. However, using the scan tool to kill the injector does not reduce rail pressure in the injector and the tip can still leak fuel, cap off lines one at a time (cap is tool # EN-47589) to pinpoint injector. Also look at the balance rates, if the tip is leaking fuel then the balance rates may be out of specification. Try increasing the rail pressure, we find injector nozzles that leak at idle pressure, but do not leak at higher pressure.
2) Check glow plug operation when cold.
3) Check rail pressure when engine is off, it should be 1.0-1.8 MPa(145-261 PSI) LB7 and LLY, or 0 PSI LBZ and LMM. Skewed rail pressure readings will usually not cause a hard start.
4) Excessive idle time can cause white smoke when cold due to carbon build up on the injector tips. More than 20% idle time is excessive. If the injectors have excessive carbon on the nozzle tip then balance rates should be high on that cylinder.
5) Some LLY engines have a reflash that addresses rough run, miss, and smoke concerns. Check to make sure the ECM is up to date.

Last edited by Rvn4me; 08-03-2019 at 04:38 AM.
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