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Thread: stumped by my CJ - any local mech's want to help out?

  1. #1
    Web Wheeler!
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    stumped by my CJ - any local mech's want to help out?

    Hey folks, need some help with a Jeep CJ - ideas or if you want to help wrench on it... i'm in Greensburg PA - here's what i've got
    77 Jeep CJ7 258 I6, MC2100 carb, HEI ignition, 5 speed

    CJ idles rough and stalls when hot. Choke is operating properly - fires right up when cold, idles pretty well but not quite smooth - gets hot and idles rough.. stumbles and stalls if i try to put it in gear and move

    New carb MC2100 - thermal choke - ran fine for a few weeks.
    new fuel pump
    checked fuel
    checked fuel filter
    checked time (as best as i could)
    swapped ignition coil, checked wiring, plug wires all seem cool, cap n rotor look good
    plugged off all the emissions components one by one to eliminate
    re-torqued manifolds and carb base- I'm still thinking vacuum leak is the problem - i see a lot of discoloration around the gaskets:
    If i close the choke manually the idle picks up and the jeep runs great. under wide open throttle the jeep runs great - let it off and it pukes. I ran starting fluid around the manifolds as well as a stethescope but i can't really discern anything...just a bit if anything..
    Anything any of you see that I missed? Anyone familiar with CJ's or know anyone in the Greensburg area that would be good to get a hold of?

  2. #2
    Right Wing Extremist! DMG's Avatar
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    Does that have a power valve?

  3. #3
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    It does - single stage - is it possible to test that? i read elswhere that the PV could be a problem.

    the only thing i haven't done is pull off the carb and blow everything out with air.

  4. #4
    Right Wing Extremist! DMG's Avatar
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    I believe you have to pull off the float bowl and Put vacuum to it to test it. It has been a while since I messed with one.

  5. #5
    If the carb runs good at WOT then it should run fine when over 1000 rpm. You may have a plugged up carb, how long has it been on the engine? Did it just start this problem, was there a noticeable change after something? I live in the Gbg area and may be able to help out.
    Which 2100 is it? The venturi id # is under the accelerator pump rod inside a circular calendar looking print. Should be 1.XX Most likely a 1.08 or 1.03 those are the popular swaps for the 258. I have a 1.08 here, but it also needs gaskets.
    72 Jeep Commando, 401, Auto, Swampers, Locked...

  6. #6
    Web Wheeler!
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    Commando,
    First of all...you've got a commando.. that rocks. those are so sweet....

    yep its a 1.08. i'm thinking carb too. the carb has been on for a month or so - but only driven about 7 or 8 times. then i tore the jeep apart to put another set of fenders on.. did a tranny swap...I drove it back and forth to work and the gym a few times, then one morning on the way to work it just started acting up when i put in the clutch to come to a stop sign..
    Starts great, idles smooth when cold (not perfectly smooth but i figure if i can get it to smooth out once warm i can take care of that)
    if i give it throttle from under the hood it's got a little stumble if i do it slow but if i kick it open it hits WOT fine. runs at higher RPM
    not at idle, not under load. I may take the carb off one night this week and blow everything out from the bottom up.. that's really all i can think of.

  7. #7
    Less posting, more wheeling!
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    How long has the HEI been in there since it started running bad? I know some of the 77's with the prestolite ignition system require a resistor wire to keep the ICM working correctly. You'd have to do a little research on this as I didn't run into that problem on mine.

    Just throwing that out there incase it's a spark problem.
    Heat the hole freeze the shaft

  8. #8
    Web Wheeler!
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    the HEI has been in for several years. one of the first upgrades i made to the CJ. i've read that sometimes the advance will get gunked up - i'm going to try and lube that up, see if it helps.. i'm gonna pick up a spare set of wires, cap etc try all the cheap/easy stuff first then i'll come back and see if anyone else has any thoughts.. thanks folks
    z

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