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1989 chevy k1500 Rough Running

Discussion in 'Chevy Trucks' started by EPS, Oct 7, 2007.

  1. EPS

    EPS Member
    Messages: 66

    I have a question. I have a 1989 Chevy K1500 which when first started runs and drives excellent! However when it warms up the check engine light comes on and runs rough what could this be? Also it will go into 4wd fine when cold but when the truck warms up if I take it out of 4wd and then try to put it back into 4wd it will not go. :realmad:

    REAPER 2000 Club Member
    from 60050
    Messages: 2,230

    Sounds like a vacuum leak some where.

    The actuator I believe is vacuum operated for the 4x4.

    Maybe when is cold the line is stiff enough to keep it sealed.

    As it warms the hose may be soft enough to open up the small leak.

    A good way to check this is by taking a propane torch turn the gas on but do not light it and run it along all your vacuum lines while the truck is running.

    If you notice a increase in idle RPM's that is the propane being sucked in the hose.
    Via the leak.

    If it is a vacuum hose leak I would go ahead and replace all the vacuum line on the truck because the other lines are just as old.
  3. EPS

    EPS Member
    Messages: 66

    vacuum leak

    Thanks for the tip reaper I will check into that. Sounds like that could be my problem.:rolleyes:
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    It definitely could be a vacuum leak causing you rough running when hot but it's isn't what is wrong with your 4WD as it's electric, not vacuum. On the TBI Chevy's, the most common cause of a vacuum leak is either the gasket between the throttle body or the intake gaskets themselves. Use the propane method like Reaper mentioned to help pinpoint it. Your 4WD problem is more than likely the front axle actuator since they are notorious for failing, especially on the 88-94 truck's. When they're failing they can do exactly what your experiencing..very slow or erratic engagement.
  5. EPS

    EPS Member
    Messages: 66

    Thanks I am going to try the propane thing and will get a new actuator as it is slow to engage. Also it goes into 4 Lo real hard I'm afraid of breaking the damn thing I have to push so hard.
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    A "hard" 4 low engagement is usually caused by rust and corrosion on the shifter mechanism under the plastic console. You'd be surprised at how rusty and corroded they get under there..
  7. cwags73

    cwags73 Junior Member
    Messages: 19

    Those transfer cases will shift hard if the oil has moisture in it as well. I have no clue how it gets there but I've changed the oil in several of them and it helped a lot.
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    They'll also shift hard if they're low on oil too..
  9. Jgrub75

    Jgrub75 Member
    Messages: 30

    If the check engine light is on there should be a code set, That will tell you what is wrong. I believe auto zone checks them for free. Let us know what they say. Sounds like it might be a coolant temp sensor.