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  1. #1

    258 cj7 rough idle; won't idle

    Starts right up, have to feather the gas to maintain a rough idle. All emissions were removed and got a weber carb with aftermarket headers and cam.

    I've done what I know to adjust the carb, and verified the timing...really rough idle. If it's the gas what can I do to be sure, and how do I fix it?

    any other ideas?
    It's beer:30 somewhere!

  2. #2
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    Re: 258 cj7 rough idle; won't idle

    What's the history - is this a jeep that ran fine until one day, or has it sat for some tmie?

    My first guess would be a clogged up carb jet
    My 2005 Wrangler Build Thread

    He who is without oil shall throw the first rod. -Compressions 8.7:1

  3. #3
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    Re: 258 cj7 rough idle; won't idle

    check for vacuum leaks
    ALL I OWN ARE JEEPS!

    54CJ3B ,76DJ5RHD , 81DJ5RHD, 88XJ , (It's)93XJRHD(Alive), 06KJ ,

  4. #4

    Re: 258 cj7 rough idle; won't idle

    If you find no vacuum leaks,I'd check the plugs. If one or more look worse then the rest you may not be getting good spark to them....check the cap & plug wires.
    Tom Landvogt
    1978 CJ5(my toy)
    2001 Cherokee Sport(winter daily driver)
    2002 Dodge Dakota(summer daily driver)
    2017 Ford Escape(wifes' driver)

  5. #5

    Re: 258 cj7 rough idle; won't idle

    <Starts right up, have to feather the gas to maintain a rough idle.

    that could be rich or lean mix, vacuum leak, or fast idle cam not involved...I need more specific info. such as "runs out of fuel and pedal squirts accelerator pump spray for engine to catch for a second"

    <All emissions were removed and got a weber carb with aftermarket headers and cam.

    details on the cam? how far from stock?
    did you seal all the emissions ports against vacuum leaks for sure?

    <I've done what I know to adjust the carb,

    depends on the jet orifaces

    <and verified the timing...really rough idle.

    book timing specs will make an engine start...depending on your spark advance and such, "on the money" final timing can be different than book spec.

    < If it's the gas what can I do to be sure, and how do I fix it?

    is it gas?
    do a compression check to test the valve seats, those numbers tell a lot, you hope to see 150 psi... 120 and below will show up as rough idle.
    get a pocket spark tester you touch to the wires from sears for $10 and verify you have good spark to all cylinders. (and good enough plugs). a night time eyeball check is good to find spark leaks.

    spritz the intake for vacuum leaks and check all vacuum hoses for dry rot, and plug threads...vacuum is critical on rusty vintages.

    if all the foundation is right, then you check inside the carb for float level. dirt, maybe loose jets... as well as the butterfly pivot for wear.

    timing by ear is retard is slow and throaty, advance is fast and thin. the advance has to working, but idle is the meaty middle part, not too retarded.

    advance and lean makes heat
    retard and rich runs cool and plugs foul.

    idle mix should be a mini-tad rich so it doesn't stall at lights, and thick enough to jump as you first open the butterfly.

    timing should be advanced enough so the engine sounds young.

    but you have to prove compression and vacuum or it's chasing phantoms.

  6. #6

    Re: 258 cj7 rough idle; won't idle

    Unfortunately I don't have the specs on the cam readily available...I do know its aftermarket and it does have a slight lope to it.

    The history on it is that it started and ran fine last fall. It has sat since October, but periodically I would go out and try to start it during the winter. I park it during the winter so this was a nomal routine for me. At some point during the winter I went out to start it, but couldn't keep it at an idle. I didn't spend any time looking at it then. Once spring came around I tried again and it still wouldn't idle unless I feathered the gas peddle.

    Last spring I went through and changed all the plugs, replaced all the plug wires, and installed a new distributer cap. Now I had other issues with the jeep (clutch), but nothing to do with starting and keeping an idle. In fact it sat for a awhile last year while I was going through the clutch issue, and it started and ran fine after all the clutch work was done.

    The bottom line is that it started and ran fine up to last fall, which is normally when I garage it. Now it won't idle.

    Thanks!
    It's beer:30 somewhere!

  7. #7
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    Re: 258 cj7 rough idle; won't idle

    I'd say a clogged idle jet in the carb. If it ran fine with that cam / headers, then they probably aren't the problem.
    My 2005 Wrangler Build Thread

    He who is without oil shall throw the first rod. -Compressions 8.7:1

  8. Re: 258 cj7 rough idle; won't idle

    The stock carb sucks put on a weber and don't look back.
    Rubicon Rich PatriotJeepers, Inc
    05 Rubicon
    86 CJ7 ,258,T18,Scout Dana 300,Dana 44's,Lockers,Twin stick,OBA,8274 Warn winch.
    51 M100

  9. #9

    Re: 258 cj7 rough idle; won't idle

    <... it started and ran fine last fall. It has sat since October, but periodically I would go out and try to start it during the winter. I park it during the winter

    any chance you have a mouse nest in the air cleaner and sucked some into the valve seats? them critters can be sneaky. I'd do a compression check to verify the seats are sealing right and stems aren't sticking...sitting can spawn gremlins.

    < I feathered the gas peddle.

    I'm not sure what you mean by "feather"...does that mean you open the throttle a bit and keep it at high idle (more air)

    or does that mean you pump it and get the advantage of the accellerator pump squirts? (more gas)

    I agree with the clogged idle jet suggestion, tho it could still be a vacuum leak on a dry rot hose.

    do you smell rich gas at idle? that could point to a spark miss, low compression (valve seat), a float with a pin hole in it, a leaky float valve and such.

    first move is verify spark, then open up and clean the carb innerds pristine with a new fuel filter.

  10. #10
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    Re: 258 cj7 rough idle; won't idle

    Are you running year old gas? If so, you may try draining that, or at least mixing half new and half old.
    My 2005 Wrangler Build Thread

    He who is without oil shall throw the first rod. -Compressions 8.7:1

  11. #11

    Re: 258 cj7 rough idle; won't idle

    The carb is a Weber. I am using old gas and that was one thing I was going to try this weekend.... I'm also going to try clearing and cleaning the idle tubes. Never done this before so this will be interesting. I said that with the clutch too, and some time later and a few cuts, bruises down the road I made it through it!

    Thanks for all the ideas, I'll let you know how it goes. Hopefully will have my toy back this weekend!
    It's beer:30 somewhere!

  12. #12

    Re: 258 cj7 rough idle; won't idle

    Well,
    The tank was completely drained, new gas put in, fuel filter changed, and all fuel hoses changed and it still will not idle on its own. I will say that it is easier to maintain the idle with the gas pedal, but it still runs rough and will not idle on its own.

    I also went ahead and checked the plugs and wires and they all looked really good. I had someone keep it running while I sprayed WD40 around the manifold, base of the carb, and egr. Nothing changed, the idle remained the same.

    I also took the top plate off of the carb and thoroughly spray cleaner throughout. I did not have a wire to use to run through the tubes though. The rest was clean to start with.

    I'm thinking spending $15 on a rebuild kit is next, but I've never done that before either, and I'm not confident enough that it will work.
    It's beer:30 somewhere!

  13. Re: 258 cj7 rough idle; won't idle

    It does not take much to clog up the Carter jets that's what's wrong.
    I'm telling you buy a Webber and your problems will be over. I run a Webber with a one line in fuel clear plastic filter. You can see the gas in it.and when it gets dirty you will see.
    Rubicon Rich PatriotJeepers, Inc
    05 Rubicon
    86 CJ7 ,258,T18,Scout Dana 300,Dana 44's,Lockers,Twin stick,OBA,8274 Warn winch.
    51 M100

  14. #14
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    Re: 258 cj7 rough idle; won't idle

    Quote Originally Posted by Rubiconrich View Post
    It does not take much to clog up the Carter jets that's what's wrong.
    I'm telling you buy a Webber and your problems will be over. I run a Webber with a one line in fuel clear plastic filter. You can see the gas in it.and when it gets dirty you will see.
    Quote Originally Posted by 05renegade View Post
    The carb is a Weber.

    Looks like he's already running a weber
    My 2005 Wrangler Build Thread

    He who is without oil shall throw the first rod. -Compressions 8.7:1

  15. #15

    Re: 258 cj7 rough idle; won't idle

    Yes I am running a Weber. I do have some somewhat good news today....I tested the compression in each cylinder and each were right at 125. From what I've read this is good anyway! I also was able to keep the jeep idling, but I cheated and used the throttle adjustment. I have to keep it at about 1100-1200 RPMs but at least its running on its own. The idle is still choppy.

    While it was running I checked the vacuum and I thought it was ok, but again I'm not that experienced with it. It fluctuated with the rpm's but for the most part it stayed within or at the edge of normal...kind of hard to tell with the rpm's where they were at.

    I did look into the carb and did not see any misting from what I thought were the idle jets. Is there supposed to be visible misting? If not, then I think you were right about the clogged jets even though its a weber. I think I am going to pull the carb and go through it thoroughly. I don't really have any piano wire to use, but I guess I can find something else.
    It's beer:30 somewhere!

  16. #16
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    Re: 258 cj7 rough idle; won't idle

    You shouldn't need any piano / guitar wire. Just get two cans of spray carb cleaner from your local parts store, some vinyl gloves, and the gasket kit for that carb. Take lots of photos before you take anything apart, so that you can make sure to hook everything up the same. Then take everything apart and clean it with carb cleaner. You'll want to hold each jet up to the light and try to look through it. If it looks clogged then just blast it with carb cleaner. Reassemble everything with new gaskets and you should be good.

    You should make sure to properly set your float. I don't know what the right height is for yours, but your kit may come with a little ruler that allows you to position the carb float correctly. Most of the time if you don't bend anything you won't have to do any adjustments on it.

    I just cleaned the three carbs on my outboard 2 weeks ago. When I cracked them open they all had stuff in it like this:
    Attached Thumbnails Attached Thumbnails 258 cj7 rough idle; won't idle-dirty.jpg  

    258 cj7 rough idle; won't idle-dirty2.jpg  

    My 2005 Wrangler Build Thread

    He who is without oil shall throw the first rod. -Compressions 8.7:1

  17. #17
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    Re: 258 cj7 rough idle; won't idle

    one other question, did you check the timing at idle, or at 1600 RPM?
    My 2005 Wrangler Build Thread

    He who is without oil shall throw the first rod. -Compressions 8.7:1

  18. Re: 258 cj7 rough idle; won't idle

    Which Weber?

  19. #19

    Re: 258 cj7 rough idle; won't idle

    I want to say its a 32/36 DGEV, but I can only go off of pictures, It was installed when I bought it, and I have no documentation. It has the electric choke.

    As far as the timing goes, it was idling but at a higher than normal rpm...about 1100. I realize it's not the right way, but I was just happy to hear it running again and I wanted to see if it made any difference.
    It's beer:30 somewhere!

  20. #20
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    Re: 258 cj7 rough idle; won't idle

    It's been years since I've timed a CJ, but I was researching your problem. Another guy said that he timed his CJ at idle, instead of the recommended 1600 RPM, and that resulted in it being 7 degrees off, and running poorly.

    I'd find the correct RPM to time the thing at (shoudl be in the engine bay) and make sure to get that down first. Do that before tearing apart the carb.
    My 2005 Wrangler Build Thread

    He who is without oil shall throw the first rod. -Compressions 8.7:1

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