Black smoke

Sounds like its running too rich

Probable causes of an engine running rich are as follows:

1. Excessive fuel pressure can be cause by restricted fuel return line
2. Defective Oxygen Sensors.
3. Leaking injectors and fuel pressure regulator.
4. Coolant temperature sensor out of calibration.
5. Restricted air intake system.

Check the fuel pressure with a gauge if its within specs-Injector/s and fuel pressure regulator could be leaking-investigate

IF the black smoke is coming from the exhaust, that tells me it is running rich (too much gas). Make sure the air filter is clean and not blocked. Also, has the check engine light come on? To me it sounds like there is a problem with the ambient temp sensor. It is a sensor that tells the computer how warm or cold it is outside and the engine temp. Based on that info, the computer determines the air fuel mixture needed for the engine to run properly. Now the idle problem you are experiencing can be caused as a result of the temp sensor or a bad throttle position sensor. As far as the EGR, it would most likely cause a rough idle, but not what you described.

LEt me know if the check engine light has come on.

Joe

Try replacing the ambient temp sensor. It tells the computer the outside temp and engine temp. As a result, the coumputer tells the injectors how rich to make the mixture. For example, if the computer thinks it -40 degrees, it will make it run really rich.

Are you refering to the mass air flow sensor? Also, the black smoke indicates a rich fuel mixture. If you are refering to the MAF, try cleaning it. They make special cleaner for them you can get at any parts store.

Also, check the converter to see if it is getting red hot.

Let me know what you find.

Joe

Actually, the grayish smoke tells me the coolant may have been getting into the combustion chamber via a bad head gasket. However, black smoke indicates a rich fuel mixture. Has the check engine light come on?

By the way, if the body is good, 97k miles isn't even broken in yet.

Let me know.
Joe

Possible causes include a bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode.

A bad oxygen sensor may prevent the system from going into closed loop, and usually causes the fuel mixture to run rich causing an increase in fuel consumption and emissions.

41- The o2 sensor is reading lean or not switching.
45 is self diagnostics.
Does your truck have a MAF sensor? Look for vacuum leaks. Does the truck miss at idle or under load?

Have you done the wires? Could be an ignition miss since it is under load. Might even be a weak injector or two