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Old 03-04-2010, 08:37 PM   #1
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Yj Problems

my 89 jeep runs and idles fine. but when i accerate it backfires through the carb. i have to accerate very slow. or else it will backfire and shut off. when in neutral it revs fine unless i go straight to the floor. then it does the backfire thing. i have no idea what this could be. carb fine tuning maybe? any help would be great thanks
-Josh

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Old 03-04-2010, 08:45 PM   #2
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Check the timing I just had the same problem today minus backfire threw carb

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Old 03-04-2010, 08:45 PM   #3
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check for gasket leaks around the intake and carb. may be timing or valve issue. check all the simple stuff 1st, wires / plugs.....

did this just start happening out of the blue?
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Old 03-04-2010, 08:58 PM   #4
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ill check those saturday. im trying to get a bunch of ideas to check out on saturday. but no its been happening for a while. slowly making me have to accelerate slower and slower. its to the point where it need to be fixed now
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Old 03-04-2010, 09:12 PM   #5
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i had idle probs and bought a new weber carb for the 4.2. rebuilt the engine before changing the carb ( actually building a project money sink hole jeep YJ that I have become obsessed with ). when i went to reinstall the intake it had a sizable piece broken off the #1 port where the intake bolts to the head. I dont know if my issues were a bad carb or just the broken intake, but from what I gather the OEM carbs are junk once the idle issues start. will be installing the new intake and carb Sat myself, hope to make some noise under the hood. good luck getting up and running. Does sound like your timing is off. check the distributor to see if its loose or turns easily by hand. maybe the locking bolt just backed out a bit and advanced timing a bit and you can time it real quick and be back up and running in minutes.
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Old 03-04-2010, 09:24 PM   #6
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I had something like that happen to also. ( but not the yj) It was the cat converter it was plugged.
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Old 03-04-2010, 09:29 PM   #7
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thanks guys. ill definatly try to check all this stuff out on saturady. i will let you know if i find the problem. KEEP THEM IDEAS COMING
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Old 03-04-2010, 11:34 PM   #8
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It's a carb. You're running too rich or too lean. Tune it. Timing is a factor. Distributor too.
Hearing the backfire is a pain in the ass, and no man alive will ever understand all the nuances of a carb...but there are 3 basic steps to take. All covered in this thread. Worst case scenario: valve work/piston rings. Best case: tuning carb, timing.
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Old 03-05-2010, 03:42 PM   #9
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the carb is less than a year old. so thats why im questioning if its the tuning of it. it said pre tuned when i bought it. but havnt tuned since its been on the jeep
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Old 03-05-2010, 05:06 PM   #10
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sound like a timing issue to me
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Old 03-06-2010, 01:14 AM   #11
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ignition coil and ecm. nutter bypass solves all your problems wont ever back fire on you

This is a Picture Guide to Nutter Bypass - JeepForum.com
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Old 03-06-2010, 06:11 PM   #12
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so i tried the nutter bypass. have done all the splicing correct along with the vacuum lines. wont fire. turned distributor as much as could and i can get a slight puhh out of the engine. the distributor wont turn anymore because of the vacuum line is hitting the engine block and wont let me turn anymore. is there anything else i can to for the timeing or am i able to somehow pass the engine block some how? thanks
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Old 03-06-2010, 08:05 PM   #13
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did you try changing the ignition coil? and made sure all your hoses are connected right
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Old 03-06-2010, 08:35 PM   #14
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the coil is pretty new. i dont think thats a problem im 90% sure its timing, i just cant turn the distributor anymore bc the vacumm hose is in the way

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