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  • '86 CJ7 - Fluctuation in idle speed - Help!

    Howdy! New to posting here, but been following for a bit. Here's my deal...
    I have an '86 CJ7, 258 I6, Stock Carb (probably my problem) lol... anyway... here recently, when I'm idling or driving at lower speeds, I lose RPM's in weird intervals. The best way I can describe it is this. Feels like the A/C is kicking on, but I don't have A/C. Literally just drops in idle, and might even be happening at higher RPM, but just not as obvious. At lower speeds, it's just crazy obvious. Do I just need to replace the carb? fuel pump? Could it be a vacuum problem? It's making me nutty.

    Thanks in advance for the help.

    T

  • #2
    i'd start with the fuel filter. if that doesn't do it, then move to a tune up.

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    • #3
      You know, I should have said what I've done so far... sorry.... I just replaced all filters, plugs and wires. Going to replace the cap also. Don't know how I spaced that... Thanks again.

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      • #4
        in that case check your choke or for a vac leak. i don't know if there's a way to test the motorcraft ignition module or not, but they've been known to go bad to.

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        • #5
          I had that problem at low speed. I went with a weber, that took care of the problem. The only downside is my exhaust smells like a 2-stroke.No matter how I adjust the mix-Idiol, it's too rich.

          cj-5 4in lift 33x12.5 mud weber

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          • #6
            Mine 'hiccupped' when turning about 1800 rpm or more. It kinda totally lost power for say, half a second, then kept going like nothing was wrong.
            It kept getting worse.. until i had to replace the stator assembly (it's in the dizzy).
            Not saying it's your problem, just a possibility.

            Most likely it's that Carter carb... or 1 of the zillion things attached to it acting up.

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            • #7
              Thanks guys.... appreciate the input. I was planning on doing some other things first, but looks like I might need to get a new carb sooner than later.
              Thanks Again.

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              • #8
                Brother in law had similar problem and after 6 months of troubleshooting found that his carb. gasket was leaking. I would also say replace all of your vacuum hoses and check their routing as well.

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                • #9
                  T5150-
                  When I had my Carter rebuilt, thats what got me to go do it.Apparently, if the carb is bad, the computer has a heck of a time making adjustments and it runs all over the RPM range. This is pretty cool, at least I can pass on stuff that frustrated the heck out of me when I first joined...we are all the same pretty much!!

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                  • #10
                    The 80's 258 had miles of vacuum lines to operate all the #%$%@# the put on the engine. Provides lots of opportunities for a nice fat vacuum leak. Also, the Carter 2-bbl that comes on your engine has a base plate that was manufactured from very poor quality aluminum. After using it for a while, the throttle bores wear out in the base plate creating a vacuum leak. The computer reads the vacuum leak as a lean charge and adjusts the idle accordingly. The lean charge returns and soon you have an engine that idles all over the place, thanks to the computer. If you buy a rebuilt Carter make sure that the base plate has been rebuilt and there is no wear in the throttle bores. I have heard from many people that they end up spending a lot of money for a rebuilt carb, only to have it runs as bad as the one they replaced.

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                    • #11
                      I wonder if that is all that was wrong with my 8. For the longest time, the engine had to warm up for about 15 mins, didn't matter how hot or cold it was outside, and even then if I got on it, sputter, cough, cough, sputter. It sucked, even after I rebuilt the carb, it still did it. Man, I could have fixed it with a simple upgrade. Well now I know, but it is in the garage for a total restoration/rebuild.

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                      • #12
                        Rochester Quadrajets have the same problem. You can rebuild the carb, put all new components in it, and still have an engine that runs like crap. Pretty frustrating. I know that some guys will drill out the throttle bores in the base plate with a drill press then install bushings to eliminate the potential for wear. Just an idea.

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                        • #13
                          Get you a can of starting fluid and start checking for leaks. It may be the carb or could be the intake manifold gaskets are leaking.

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                          • #14
                            Great stuff guys... I appreciate it a lot. Going to spend some time on it this weekend. Again, thanks very much.

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                            • #15
                              Oh and just to let you know if the manifold has never been off there wont be a gasket in it. You can get them from the parts houses though.

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