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Manifold Heat Control?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by civicstomper, Jan 28, 2004.

  1. civicstomper

    civicstomper 1/2 ton status

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    Hey. As some of you may know, I have an 87 K-5 with a 350 TBI. It has been stalling out whenever I go slowly up or down a hill backwards and sometimes jsut when driving very slow. The odd thing is that it almost always starts right up afterwards.

    I was told to check the sensors, which I did by lifting the codes. all turned out ok. What I did find was that when the previous owner had replaced the spark plug wires, they put most of them in the wrong places. I was suprises it ran so good this way, but when we checked the firing order, they we wrong. after fixing this the truck seemed much better, but a few minutes later it was having the same problems. /forums/images/graemlins/frown.gif

    My friend thought it was the IAC, so he took it, checked it, and put it back in, and now it idles much lower, and I have to get it back to were it was before.

    Anyways sorry to go off on a tangent; he is wondering if these trucks were supposed to have something called a Manifold Heat Control, or something along those lines. I looked for it in my Hayes manual, and I couldnt find anything on it. Does anyone know if there is something like that on these trucks, if it has a different name, or anything about it? This problem has been bugging me and I just want to get it to the point were I can take it on trips without worrying about it.
    sorry for making this such a long post, I just didnt want to leave anything out.

    Any information or advice would be greatly appreciated, Thanks!

    -Pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    If the IAC was screwed with, I believe the proper procedure would be to remove power to the ECM (Pull the fuse) for 10 seconds or more, then replace the fuse, and go drive it. IAC needs to "learn" the correct position, needs to be driven for this. May or may not be the reason you are now having low idle problems, but since IAC was screwed with, and it has idle problems...

    No manifold heat control. There is an ECM temp sensor for the engine, but thats it. Sounds to me like *perhaps* something in the tank is limiting fuel flow, maybe the baffle has broken. Extremely typical for the baffle to break, although I don't think many people even notice.

    The problem occurring on an angle is what makes me suspect this. If it was an electrical/sensor issue, the problem would be constant. (and not be repeatable only because the vehicle is at a certain angle or driving at a certain speed.

    Lot easier to do on TPI, but I'd probably be monitoring fuel pressure when this is happening. I'd hate to say jump in and pull the tank, but I can't think of anything else that would be related to angle except fuel delivery. Nothing else cares what angle the truck is.
     
  3. civicstomper

    civicstomper 1/2 ton status

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    Hmmm, so you're saying it would be a good idea to replace the fuse in the ECM? That doesnt sound too hard, and if thats all it needs, then that would be cool.

    I hope that its not something in the gas tank, only because I just put the new fuel pump in and its not a fun job. If it is, then I will do it but I am hoping the fuse will fix the problem.

    Thanks for the help, and I will let you know how it goes /forums/images/graemlins/thumb.gif
    -Pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, I'm not saying replace the fuse, just pull it, wait 10-20 seconds, then reinstall it. That kills power to the ECM.

    The ECM "learns" where the IAC needs to be, I would have to imagine that cleaning it may have changed where it "needs" to be, and the ECM needs to re-learn that.

    When you had the tank out to replace the pump, did you notice that the black plastic baffle at the bottom of the tank was loose or not? It should have been really obvious. Since you replaced the pump, did you drain it really well to make sure there was no water in there?

    Have you taken any hard hits or slammed on your brakes since replacing the fuel pump? That will also break the baffle, and if it wasn't when you replaced the pump, thats about the only way it would now be broken.

    Just sounds like a fuel issue to me, at least the stalling part. Could very well be something in the ignition though, but that doesn't really answer the "easy restart" condition.
     
  5. civicstomper

    civicstomper 1/2 ton status

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    See, I have never actually done anything with the ECM, so I wasnt sure if the fuse needed to be replaced with a new one. I actually dont remember seeing anything loose at the bottom of the tank. It wasnt really the best conditions and it was my first time, so I may have over looked something.

    I will definitly try the fuse, that would be great if that was all I needed to do. Like I said, after replacing all the plugs and spark plug wires, distributor, rotor, fuel pump, fuel filter and fuel lines, I dont know of much else that could be doing it.

    Thanks again for the help, I will try to let you know how it turned out as soon as I can. Thanks again! /forums/images/graemlins/thumb.gif
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  6. civicstomper

    civicstomper 1/2 ton status

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    well, I disconnected the fuse and then replaced it after 30 seconds, and I drove it. The idle does sound better now, but it still stalls out on me. Its wierd though, because for the first 10 minutes or so it ran great. I would give it a lot of gas, and it came down like normal.

    Then instead of coming down, it would start to sputter a little, then correct itself. The more I drove it after this point, the worse it got. Although one thing I may have noticed is that it may not be stalling because of the incline, but just as a result of me trying to give it more gas.

    After I was done, I checked for codes, and now I am getting a code 45, which is the Oxygen sensor. I'm not sure how the two of these problems are related, but I am going to get a new o2 sensor.

    I will see if the new sensor makes a difference. Thanks for the help with the Idle, it sounds much better now /forums/images/graemlins/smile.gif. I'm not giving up on it yet, its getting closer to being done everyday. Thanks for the advice, and I'll keep you updated.

    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     

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