1990 Jeep YJ issues, HELP!!!! Carb, back firing... - Jeep Wrangler Forum
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Old 06-02-2013, 10:08 PM   #1
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Angry 1990 Jeep YJ issues, HELP!!!! Carb, back firing...

Ok, so I have a 1990 Jeep Wrangler Laredo, 4.2 I6, recently done:

-complete tune up, plugs, wires, cap, rotor... has msd ignition, accel distributer and msd ignition coil.
-has brand new weber carb with snorkel, most vacuum lines replaced

Exhaust had several leaks, and fell off one time which forced me to replace it. Pace setter headers now. Most of the work was sparked from loss of power, backfiring thru exhaust and carb and sluggish ride. Had no cat and little to no emission control, its a woodsing vehicle. motor was rebuilt and has about 85k on it now, still runs strong.

Loss of power (currently)- steady acceleration, slowly, goes ok. If you stomp it or do steady acceleration, but rapid, it falls on its face (bogging down) then after about a second, second and half power comes back and it takes off. Sometimes you will here a slight back fire or a nice one. No clue what else i can do to correct this, fuel pump? I still have what appears to be a exhaust leak somewhere near headers, maybe manifold? so is going back to shop tomm. Downshifting will popp, and at times when you shut off, but happens more after longer rides. Could the existing exhaust leak continue to do this?

Anyone have ideas or even similiar issues?

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Old 06-03-2013, 06:27 AM   #2
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Spray some carb cleaner into the fuel bowl vent, don't stick the hose all the way in, but partially in, then spray, pump the accelerator a couple of times, and start it up.

Something is leaning it out on WOT and causing it to stall. Could just be in the fine adjustments, or be dirty inside. Change the fuel filter?

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Old 06-03-2013, 10:59 AM   #3
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New fuel filter
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Old 06-03-2013, 11:11 AM   #4
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So as soon as you mash the gas, it bogs down/cuts out for a couple of seconds, and then goes again correct?
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Old 06-03-2013, 12:06 PM   #5
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Sounds like the accelerator pump on the carb not squirting enough fuel, may need to check the accelerator pump, check ball and fuel float level for proper operation may have gum build up, you need to disassemble the carb and clean/replace seals check all passages are clear/clean
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Old 06-03-2013, 01:38 PM   #6
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Agreed. I was just about to come back in here and type the same thing as I have been taking carburetors apart and putting them back together this weekend. lol
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Old 06-03-2013, 03:36 PM   #7
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As long as you're 100% sure you no longer have an Ignition Control Module I would go with LUIS and indirocz.
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Old 06-03-2013, 04:54 PM   #8
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Carb has maybe 700 miles on it. Exactly u mash the gas, bogs then takes off. Seems more when lower rpms, 2500 amd higher ifnu mash usually takes right off. Same when idling. If mash in nuetral same issue unless rpms up
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Old 06-03-2013, 05:58 PM   #9
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Yeah, sounds like your float or needle may be sticking in your carb.
How long has it been sitting?
There are a couple of tiny filters inside the carb that can gum up, a

Do you maybe have some bad gas in it?
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Old 06-05-2013, 02:19 AM   #10
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Carb has done since bramd new. Its a weber actually third one on there, returned 2 thinking was defect
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Old 06-05-2013, 06:24 AM   #11
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Double check for vacuum leaks

Adjust the float in the carburetor a little bit. Make sure the needle isn't getting hung up in the seat.

Possibly adjust idle mixture screws, as sometimes they can have a slight effect just off of idle when opening the throttle.

Maybe google search or youtube something about "Tuning weber xxxx" where xxxx is your model number.

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