Question about 2000 Chevrolet 2500

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I have a 2000 Chevy 2500 diesel 2wd and when I start it the rpms jump up and down,and black smoke out the back. I was told to clean the throttle body but it is drive by wire, any ideas, the peddle doesnt react. Please help

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  • garthb Jul 20, 2009

    Thanks for that reply. Just to be sure I would like to explain the whole thing, my wife drove the truck for 40 min, she parked it and came out 1 hr later, when she started the truck the rpms shot up to red line and stalled, she tried again and the same thing happened. She called me and i told her to try giving it some gas to keep it running, she did so but all it did was sputter rpms up and down and died. When i got there i started the truck, threw it in gear and it pulled me around the parking lot rpms up and down with my foot on the brake. i shut it down and left it there overnight, 24 hrs later iI went to try to start it and same thing rpms red line and die. This whole time black grey smoke every time i start it. My mechanic tried starting it and giving gas to keep it running but the pedal wouldnt respond, he thinks and GM thinks it is the drive by wire (throttle pedal) or module.Should I stick with your first response or try something else? Thank you soooo much

  • garthb Jul 20, 2009

    Thank you very much, keep up the great work



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Is this on a cold start??
I would assume it's the grid heaters cycling.
What is the RPM differential (high 7 low)

Or all starts??
Then your IP (injector pump) has probably sucked up some crud or maybe the lift pump isn't keeping the supply steady.

The MAF (if equipped) could be sticky too.

If you don't know when the injectors were last changed then they need to be changed. They are a wear item that can cause smoke and misfire.

Black smoke is the most common emitted from diesel engines and indicates incomplete combustion of the fuel. Black smoke causes can vary widely and include ..
· Incorrect fuel injection timing
· Dirty or worn fuel injectors
· Over fuelling
· Faulty turbocharger, or turbo lag
· Faulty or dirty exhaust gas recycling (EGR) system
· Incorrect valve clearance
· Incorrect fuel to air ratio
· Dirty or restricted air cleaner systems
· Over loading the engine
· Poor fuel quality
· Cool operating temperatures
· High altitude operation
· Excessive carbon build-up in combustion and exhaust spaces

Black smoke can occur across the entire operating range, but is usually worst under full power, or during the lag before the turbocharger boosts air supply to match the fuel usage such as in the early stages of acceleration and during gear changes. Moderate turbo lag smoke is acceptable; otherwise black smoke should be hardly visible in a correctly running engine.

My money is on the IP.
Check it out.

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Posted on Jul 20, 2009

  • blueextc3221
    blueextc3221 Jul 20, 2009

    Ok - now its becoming more clear with a better explanation.

    Yes - it seems your pedal module is to blame (sticking).

    Otherwise called ETC (Eletcric Throttle Control) - you called it Drive by Wire.

    The ETC should be inline with the accelerator pedal harness - and not difficult to swap out yourself.

    The black smoke is excess diesel burning off from the added strain on the motor.

    You're on the right track

    Good Luck!!



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