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No power

Discussion in 'Chevy Trucks' started by nate456789, Dec 26, 2009.

  1. nate456789

    nate456789 Senior Member
    from Indiana
    Messages: 194

    My 95 k2500 with a 350 is acting up.
    It did this once before when it was raining and sitting for awhile.
    That is why I am suspecting a sensor is going bad or acts up when it's damp.

    The truck doesn't really have any power under 40 MPH. If you hold the throttle steady the engine revs up between 1200 rpm to 1800 rpm repeatedly. Like a pulsing.
    Push the pedal to the floor and it will accelerate. It doesn't die out.
    When it gets good and hot it is not as bad as when it is cold.

    Any body have an ideas? I really think it is a sensor going bad but not sure which.
    Sometimes when the truck is first started the check engine light will be on and the engine will stay at fast idle. Even after the engine is around or above 100 deg.

    I did a code check and it just flashes code 12 which means everything is good with diagnostics and no failure code follow the code 12.

    Thanks for any thoughts.
  2. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Sounds like since it does this when wet/cold possibly have a cracked distributor cap. You may not be able to see it, but a hairline crack will allow enough moisture inside to cause issues.
  3. nate456789

    nate456789 Senior Member
    from Indiana
    Messages: 194

    Yeah last time it did this I replaced the cap and rotor and spark plugs. (6 weeks ago)
    It seemed to go away but here it is again when it has been raining and snowing for couple days.

    What is odd is the pulsing in rpm. It is consistent. Like the computer is confused.
    So it's not like it is missing out and studdering.
    I am going to clean all of the grounds on the motor and cross my fingers.
  4. RichG53

    RichG53 PlowSite.com Addict
    Messages: 1,135

    Check your air filter maybe it's getting wet....From water leaking in
  5. Blaine4450

    Blaine4450 Member
    Messages: 32

    Check your igntion control module. Had almost the same thing happen on my 92 1500, The module was around 40 bucks.
  6. nate456789

    nate456789 Senior Member
    from Indiana
    Messages: 194

    Thanks for the tip. I bought a new module - just need to install it now.
    What is really weird is When I pulled it into my 65deg garage to clean the grounds, it was fine after that. I drove it all day yesterday and I had no problems. Thought it was fixed.

    It sat for about 8 hrs and we plowed all night starting at midnight. It was about 18 deg and it did it again from the start. I thought well after we run it awhile it will go away. But it lasted all night long.
    My driver said it was fine while plowing - never missed a beat - but going to different sites it was acting up while driving between 20 and 50 mph.

    Hopefully this module will do the trick.

    What were the symptoms of your truck? I thought that the module either worked or it didn't. I have not really heard of any stories of it kind of working.
  7. Rabbitiswise

    Rabbitiswise Junior Member
    Messages: 13

    I am having the exact same thing with my 94. Driving me nuts. I put my scanner on and it was only reading 12.9 volts by the ecm. I know GM can be temperment with the voltage. Let me know if the mod works.
  8. Blaine4450

    Blaine4450 Member
    Messages: 32

    My truck would almost act like it wasnt getting fuel when i got on it hard or even just taking off from a stop sometimes. Sometimes the truck was fine for a few days then it would act up again, especially when it would rain.
  9. nate456789

    nate456789 Senior Member
    from Indiana
    Messages: 194

    Well mine is definately a moisture issue.
    Took my truck for a drive first thing this morning and it drove fine. No issues.
    It was about the same temp as the other night.
    Only thing in common between the last 3 times is rain and snow.

    I changed out the module. So we will see the next time it rains or snows.
    If it does it again I am going to change the spark plug wires next.
    So all of the ignition stuff would be new at that point. Cap, rotor, module, and plugs.
    Hopefuly this module is it. All of the grease on the bottom was burned away from the heat and the connections inside the cap to it were green from corrosion. So it has to be better now.
  10. Blaine4450

    Blaine4450 Member
    Messages: 32

    Well hopefully that does it for you! keep us updated.
  11. Rabbitiswise

    Rabbitiswise Junior Member
    Messages: 13


    Well I inspected and check out my Distributar, Look great(infact looked brand new,begins i replaced it in august), Cleaned sealed grounds. I than hooked up my scanner and going threw some trouble shooting, i found that my IAC(Idle Air Control) was just out of specs. Replace it. runs good now. Now just have to replace U-joint, Transfer case, and Exhaust donuts, and i'll be all set...lol
  12. nate456789

    nate456789 Senior Member
    from Indiana
    Messages: 194

    I could never get my scanner to communicate with the ECM in my 94 or 95.
    It said in the instructions that you could watch sensor values realtime. And transmission data.
    What brand of scanner are you using?
    Was there any tricks to get it to connect?
    96 and up is no problem connecting and watching realtime data.
  13. Rabbitiswise

    Rabbitiswise Junior Member
    Messages: 13

    mine is a snap on scanner. I'll have to get it from the truck to tell you what series.
  14. Rabbitiswise

    Rabbitiswise Junior Member
    Messages: 13


    Well I officially fixed it. I have Power again. I went threw and cleaned the mounting point of the coil, Pulled the Modular out and re-greased, and Replace the Vacuum line from TBI to MAP, and Replace Vacuum line from PCV to TBI. Runs and Idles nice and smooth. Hope this helps you guys out.

    nate456789: My scanner is a Snap on Graphing Scanner PN#MTG2500 its an older model I believe.

    Now I just have to let the For Head heal and get ready for the snow coming this weekend.