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Hesitation and low power. I have done EVERYTHING!

Discussion in 'General Chevy & GM Tech Questions' started by moogvo, Aug 22, 2012.

  1. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    Ok, so I have a 1995 K1500 5-speed, 4.3 V6. It has low power, particularly in 3rd and 4th gears. It is somewhat noticeable in 2nd gear from time to time.

    So far, I have replaced the following: fuel pump, fuel pressure regulator, dismantled and cleaned the TBI. Fuel filter, plugs, wires, cap, button, knock sensor, coolant temp sensor, distributor, cleaned all electrical contacts, checked TPS on a scope.

    It doesn't matter if it is in closed loop mode or not. It is MUCH more noticeable when running the A/C. I also notice the presence of gas on the inside of the air cleaner lid. I have replaced the MAP sensor, EGR valve, EGR solenoid, coil...

    I have no check engine light warnings. I am totally stumped on this one.
  2. Big_Mike

    Big_Mike Member 100 Posts

    Before I attempt to give any advice, let me ask... How many miles does the engine have on it?
  3. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    177k miles.
  4. Big_Mike

    Big_Mike Member 100 Posts

    Let me just say, I'm no master mechanic, but I know a few things about automobiles... I'll try to give some decent advice. Remember that the internal combustion needs three things to run optimally: spark, compression/air, and fuel. A problem with one will cause poor operation (just put that out there for the record). I am wondering if there is adequate fuel pressure. I read that you replaced the regulator, but without enough pressure being supplied, the engine could perform poorly. You may want to check that to be sure (restrictions in fuel lines like dirt can be culprits). Next is compression as a possibility. Not enough can cause operating issues as well. It sounds like you went over the ignition system fairly well, but just to make sure, did you check/set the plug gap to spec? Hope that helps... Maybe it will give you something to think about.
  5. Big_Mike

    Big_Mike Member 100 Posts

  6. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    Thanks mike. I have a new fuel pump on there and the pressure is within spec... 13 to 15 psi. (remember that this is a TBI unit). I checked the lines while installing the pump and they were clear of obstruction.

    I have not done a compression check, only because the problem is intermittent. I am beginning to suspect the cat.

    Thanks for the ideas. Please don't give up!
  7. MTM

    MTM Rockstar ROTM Winner 100 Posts

    Does yours have a MAF sensor?
  8. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    No. It has MAP sensor... A nice, shiny NEW one, I might add. :money:
  9. MTM

    MTM Rockstar ROTM Winner 100 Posts

    I didn't think so. Well I had a similar problem with mine where it just had no go what so ever and it ended up being the mass air flow sensor. Only other thing i could think of would be a plugged cat.....or slightly plugged cat
  10. Blazer454

    Blazer454 Member

    So when you say "low power" what does it feel like? Missfire, engine tries to die, or engine seems to be struggling to move along? You say it is more noticable in higher gears, is this an auto tranny?

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