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Stutter in acceleration

717 Views 2 Replies 2 Participants Last post by  GeeAea
I have a 77 CJ5 with a 304 V-8. It has the stock motorcraft carburetor, hedman headers, K&N airfilter, T150 manual transmission, stock dana 20 Transfer case, etc. It has been converted to a manual choke. The Motorcraft 2100 2 bbl carburetor seems to be in perfect condition. Everything seems to be in adjustment, and working fine. When the engine is below 1000rpms, if you step on the gas with any force, the engine stutters and stumbles (irregardless of what grade gas it is running). If you stomp on the gas, it occasionally backfires. Over 1000rpms, it runs like a clock. If I pull the choke out and then step on the gas, the problem is solved…but by smelling the exhaust, it is clear that the engine is running way too rich. And pulling the choke usually means that the engine won’t drop below 1000rpms at idle, anyhow. My first guess was to check the accelerator pump, the timing, and the mixture, but all seem to be fine. Any other ideas on what could be wrong? I have read a great deal about Jacobs ignitions (along with its various counterparts, DUI, etc.). Would such an aftermarket ignition possibly cure this problem?

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just my 2 cents, i'm not real familiar with the Motorcraft 2100 2 bbl carburetor but if you think the accelerator pump is working good, i would mess with the "idle mixture" screws, more gas (they work with the accelerator pump to cover up that off idle bog) also alot of 4 wheelers like the fuel levels in the bowls as low as possible, maybe try to adjust the float level to bring the fuel higher.

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I too am not acquaited with your carb ..... sure sounds like the accellerator pump... since it's a lean condition....but you're sure that this is in working order. BTW how is the accell pump actuated on that carb?......external rod?.....adjustable....maybe a longer stroke....bigger squirt??. Just for speculation have you tried playing with the timing.....maybe. You obviously have something wrong in the idle/transitional circuit of the carb ...... does your carb have the little vertical slots that span the bore just above to just below the throttle plate.(these are for that "transition")..and how's your throttle bore alignment? Have you played with the timing just to see the effect?

Where's dorfs when you need him?

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