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Odd idling problem, need advise

Discussion in '40- & 55-Series Tech' started by DieselFJ, Aug 21, 2006.

  1. DieselFJ

    DieselFJ

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    I have never encountered this problem before, so I hope someone else has or at least has an idea. The problem is on my 79 FJ55, which is all stock including emissions. Here is the problem. The Cruiser starts great and idles like a champ. I am able to push the choke in and drive, or let idle and it is as smooth as any 2F I have been around. The problem occurs after the pig gets hot. I can drive it around for a while, but once hot it will quit idling. It shuts off like I turn the key off. I can start it up again, but it will not idle. Once I let it sit for a while it will start up and idle fine. I have rebuilt the carb, put a new fuel filter and pump on, and I have put all new vacuum lines on. I have also put new cap, rotor, plugs, and wires on. I don't believe it is fuel because the float level remains in the middle of the glass all of the time.

    Here is what I think it might be. I believe the igniter or coil is heating up causing the problem. I have checked both the coil and the igniter according to the factory manual, and yes they are out of spec. I will replace them as soon as I can. What I was wondering is if this has happened to anyone else, or has anyone else heard of anything like this. If anyone has had this problem, or has any other ideas of what it might be, please chime in.


    Thanks
    Scott
     
  2. Pin_Head

    Pin_Head

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    I'm guessing that it is a sticky EGR valve. In '79 the EGR outlet connects to the manifold and when they stick open, they cause a vacuum leak which is a big problem at idle. If it was an ignition problem I wouldn't expect it to be a problem only at idle. Try cleaning the EGR actuator rod with carb cleaner and lube it with graphite.
     
  3. DieselFJ

    DieselFJ

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    I have seen that problem before, so I disconnected the line going from the EGR Modulator to the top of the EGR valve. I belvieve that should eliminate any EGR problmes, but I may be missing something. Please keep the ideas comming, I am stumped.

    Thanks
    Scott
     
  4. John Smith

    John Smith In the garage

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    My EGR stuck open and the modulator had no effect.
     
  5. Pin_Head

    Pin_Head

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    Bad intermittent idle fuel solenoid or circuit.
     
  6. DieselFJ

    DieselFJ

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    For the EGR I blew into the top of the EGR valve to make sure it was released.

    As for the Idle Fuel Solenoid, I will check the FSM and troubleshoot as per instructions. Is there anything that is a common failure with this system?
     
  7. John Smith

    John Smith In the garage

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    The solenoid usually has the ground wire go bad, at least that is what took out mine. I patched in a new wire grounded to the fender to fix it. I remember Jim C writing years ago that it is always the wiring that fails.
     
  8. DieselFJ

    DieselFJ

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    Well, with your help I have found the problem. The problem was one of the wires that come out of the idle solenoid. I traced the wires back to the ECM where I noticed the White/blue wire entered the clip that went to the ECM box. I am not sure where the black/white wire went, but it was not necessary to trace that wire any longer. I found that the white/blue wire that pluged into the connector that went to the ECM had broke right at the pin. If I moved the wire back and forth I was able to get the solenoid to engage. Now all I need to do is strip the wire back and reset the wire in the pin, and plug it into the connector, problem solved.

    Thanks again for all the help and advise. I feel that this is why this board is so important. Yea it is nice to discuss how tires and lifts will look and what color a Cruiser should be painted, but to be able to help with a technical question and stay with it until the problem is fixed is extremely valuable.

    Thanks
    Scott
     
  9. DieselFJ

    DieselFJ

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    Update

    I just thought I would update my thread and let everyone know of a potential problem with their ECM. After I cut the white/blue wire and began to examine the wire I noticed that the wire really looked ok, so I decided to replace the pin and a small section of wire just to be safe. I put everything back together and found that the problem was still happening. I noticed that if I pushed on the clip I could get the Cruiser to Idle, but once I let go of the clip it would die again. I looked at the clip and everything looked fine. At this point I decided it must be the ECM, I had a spare and decided to put it in. I figured I wouldn't have the problem anymore once the other box was in, but I still did. I decided to take the ECM apart and inspect the circut board to see if I could find any issues. This is where the culprit was hiding. On both ECM's circut boards the solder around the pins where they entered the board had cracked. The only pins that had cracked were the ones that went to the clip. I believe the weight of the pins over time caused the solder to crack. I re-soldered the pins on one of the boards and put it back on the Cruiser. I have not seen any signs of the problem yet, and I can wiggle the wires and the clip to the ECM and not see any issues. I just thought I would let people know in case someone else is experiencing the same issues

    Thanks
    Scott
     
  10. Pin_Head

    Pin_Head

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    This is a common problem. I have had to resolder my ECM. Vibration and the large size of the plug kills them. If you hadn't mentioned that the problem was heat related I would have suspected this first.
     
  11. DieselFJ

    DieselFJ

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    Yea, since it was such an intermittent problem I was just trying to associate the problem to anything, and the temp seemed to be the only thing. Anyway, thanks for you help, It would have taken me many more days of troubleshooting before I ever got to this point.

    Scott
     
  12. RumBum

    RumBum SILVER Star

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    I just figured out (I think, so far so good) what my idle problem has been. When I wiggle the green plug(s) on the front of my carb (idle solenoid I believe) you can hear it clicking (engaging & disengaging?). I traced and figured out the problem was in the plug itself. I need to fix that problem. Is there any reason that plug is so big? Is it insulated? Basically, would I harm anything by putting a couple male & females on each side of the connection? Otherwise, do I need to replace it with a factory type plug?
     
  13. John Smith

    John Smith In the garage

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    It is just a normal factory plug. It may be corroded, and if so the wire itself may be toast under the insulation. If the wire is good you can replace with weather-pak or other terminals.
     
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