Hesitation under acceleration

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Jesus_man
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Hesitation under acceleration

Post by Jesus_man »

I've been noticing a new problem recently on my bronco. I believe it started last summer. But I've really only put on 200 miles since then. Anyway, as the engine warms, the issue seems more noticeable.

As I accelerate moderately in the longer gears, the engine picks up rpms slowly, but if I press the pedal a little harder, it doesn't seem to pickup rpm's any faster for a second, and then something changes and it will begin to accelerate harder. Like the air supply is closed off for that second and then the butterfly opens and she charges with full power. You will really notice this on the highway as you modulate the pedal to maintain speeds up slight hills etc. It feels like it doesn't want to accelerate and then it'll charge ahead like it should.

My memory is fuzzy, but I believe I've had this issue in the past, prior to the recent rebuild and engine harness. I could be wrong.

I wish I could blame it on turbo lag, but no forced induction here, but a similar feel.

Where should I start looking?
1973 Bronco, 351 SEFI, Locked, discs, 35's ZF-5spd and Atlas 4spd. 235:1 Crawl Ratio. It may be ugly, but it's slow.
http://www.ucora.org
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Digger
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Re: Hesitation under acceleration

Post by Digger »

You might check for fuel line restrictions. Clog filter, pinched line.

Probably worth checking the regulator (via pressure gauge). Maybe its slugish. Quick tip-in's require lots more fuel cruising or slow tip-in's
Cummins R2.8 diesel, ZF5, AtlasII, HP44/BB9, ARBs, coiled / linked suspension, 37" KO2s, full cage, bumpers, etc.
Build Thread: http://www.coloradoclassicbroncos.com/viewtopic.php?f=3&t=5420

Average 23.5 mpg, Best tank: 26.3 mpg
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Jesus_man
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Re: Hesitation under acceleration

Post by Jesus_man »

I'll check the fuel system, but I believe it to be ok, only because last year I had lots of fuel issues and I replaced the filter, moved pumps around, replaced the fuel reg etc.
Thanks for the tip!
1973 Bronco, 351 SEFI, Locked, discs, 35's ZF-5spd and Atlas 4spd. 235:1 Crawl Ratio. It may be ugly, but it's slow.
http://www.ucora.org
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Stubborn3
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Re: Hesitation under acceleration

Post by Stubborn3 »

I had the same issue though not fuel injected, cleaned out lines and new filter which was needed anyway but in my case it was a heat issue so I insulated my fuel lines and that fixed it. Doubt thatΓÇÖs your issue but just tossing it out in case
'72 sport, 351 Cleveland, NP435, twin-sticked 20, unknown lift- if any, 35" KM2s siped by B.O.B, custom rust and dents, 2 kid seats.
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Jesus_man
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Re: Hesitation under acceleration

Post by Jesus_man »

Vapor lock is always something to watch out for but I don't think my temps are warm enough for that to be a concern. I appreciate the brainstorming in any case.
1973 Bronco, 351 SEFI, Locked, discs, 35's ZF-5spd and Atlas 4spd. 235:1 Crawl Ratio. It may be ugly, but it's slow.
http://www.ucora.org
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