1994 GMC C1500 smoke signals

  • 1994 GMC C1500
  • V8
  • 4WD
  • 183,924 MILES
My 1994 GMC sierra SLE z71 has been having a few problems lately, when I rev the engine when it is warmed up it emits black smoke and when I start it I get a blue smoke from the right hand side of the engine (it has dual exhaust), I also get a egr trouble code every once and a while. I have also been getting poor mileage when a few months ago I was getting 14 in town and 17 on the highway (not bad for a 4x4 with 33 inch mud tires). The engine has headers, a cold air intake, a throttle body spacer and the throttle body has been smoothed out. It has a new distributor cap, rotor, accel super stock wires, AC Delco plugs gapped at 0.35 and an MSD blaster coil. There is also a motorvation chip in it. THere is a new fuel pump, tank, IAC, TPS, MAP, O2, EGR control, temperature sensor, all have been replaced over the course of a year and a half. I made my own adjustable fuel pressure regulator but did not change the diaphram. What to you suggest that the problem could be?
Do you
have the same problem?
Monday, February 18th, 2008 AT 11:16 PM

1 Reply

I assume the engine is a 350. Is the engine a vortec? Does it have a TBI or CPI fuel injection system? What is your fuel pressure?
Blue smoke is oil being burned in the combustion chamber--Black smoke is a fuel rich condition or too much fuel squirting into the combustion chamber. Oil can get into the combustion chamber two ways--through the valve seal or through the piston rings. The valve seals are not as much as a problem as the piston rings. Do a compression test on all the cylinders and let me know what you find?
BTW--check the plugs tell me what they look like?

Oh yea, try opening the gap on these plugs to 45 or 50 thousandths. A high power coil and ignition system usually needs a bigger gap.
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Monday, February 18th, 2008 AT 11:31 PM

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