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Old 04-01-2012, 05:13 PM   #1
Shtewy's Avatar
Join Date: Feb 2012
Location: I live in Candor, NY
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Question Acceleration problems under "load"... Help please

Hi. I'm new here, and I have an '88 Wrangler with a 4.2 6 cyl., Weber Carb. I bought it used about 2 months ago from a dealer and got taken. I had to put a new motor (marshall engine), new starter, fuel pump, alternator, radiator,thermostat and housing, cap, rotor, plugs,and wires and had to pick up a new/used intake manifold. The garage finally got it all changed and running. My problem is it runs fine on flat roads, gets up to speed fine if I'm not getting on it, but when I'm going up a hill or trying to accelerate quicker, it spits and sputters and runs rough and sometimes "pops" back thru the carb or exhaust... (I'm not sure which) I would like to improve it's performance so I'm not afraid to take a long trip through PA hills to visit my daughter. Any help is greatly appreciated. Thank-you

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Old 04-02-2012, 08:06 AM   #2
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Location: Raleigh, NC
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Makes a big difference where it is 'backfiring' from, as they indicate opposite problems, for the most part.

First priority is to check your ignition timing. It's very easy to set, but you do need a special tool to do so, a timing light. If none of your buddies has one & knows how to use might want to post on your local 4X4 board & ask to borrow one.

Weber carbs tend to like a specific fuel pressure, too much & they run rich, which will cause your symtpoms & a backfire out the tailpipe. Especially if your timing is off. The solution is an inline fuel pressure regulator which can be had for about 25 bucks. Super simple install.

Tho not likely w/ a new fuel pump, you can also be getting too little fuel, which will cause a 'pop' thru the carb.

If you can, pull a spark plug. If the white insulator portion near the tip is darkbrown/black...then it's too much fuel, if it's white/blistered, then it's too little.

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Old 04-02-2012, 07:10 PM   #3
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Join Date: Feb 2012
Location: I live in Candor, NY
Posts: 6
Thanks Man! Will pull plugs out tomorrow and see what I'm looking at. The Garage set the timing and they had to advance it a little to get it to start without any problems. I'll check the timing again and see where I'm at also.
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Old 04-02-2012, 07:13 PM   #4
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Join Date: Feb 2012
Location: I live in Candor, NY
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I should say too, that the reason I'm not sure where the poppin' is coming from is because it sounds like from under the hood/down by my feet. The jeep has stock exhaust with the pump lines capped off and has been repaired before the Cat where it had broken.
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Old 05-20-2014, 12:12 PM   #5
Join Date: May 2014
Location: Houston
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I have a 91 jeep Comanche Eliminator truck straight 6 and i have popping from my carb and no power at first but slowly it starts coming back. i might be able to get it up to 35. if i put it to the floor it just pops and bog's down. It has just right at a hundred thousand miles on it. any ideas. thanks
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