Sudden loss of power at take off with initial slight press of pedal...need help - JeepForum.com

 
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post #1 of 4 Old 03-03-2013, 09:02 AM Thread Starter
dnjeep
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1976 CJ5 
 
Join Date: Feb 2012
Posts: 98
Sudden loss of power at take off with initial slight press of pedal...need help

Problem:
(This has happened since I've owned the Jeep)(Motorcraft 2100 & 304)('76)
- Happens primarily in the lower gears (not as noticable in 3rd or higher RPM & speed)
- Most noticable when starting in 1st gear from a stop
- When first pushing the gas pedal in feels like there's a catch or binding that you have to push the pedal through and the rest is free flowing (keep in mind we're only talking about a no more than 1/2 inch distance it feels like
- In this gap the engine feels like it doesn't gets fuel or air (which makes it feel like the power suddenly drops of...litterally feels like it would stall if you kept the pedal in that position and didn't keep pushing the pedal through that "zone")
- This problem only seems to happen in gear and under load (does not really exist in nuetral...but I will check that to make sure)

What I've checked thus far:
- I checked the pedal linkage and throttle cable to carb (when disconnected from throttle linkage @ carb the cable & pedal move without any resistance and moves in-and-out freely)
- Engine off & throttle cable disconnected: moving the throttle linkage @ the carb by hand results in no resistance or any binding. It moves just fine.
- Keep in mind I have rebuilt this carb completely 2 times (this has happened during this whole time before and after rebuilds)

Ideas:
I have noticed when engine running there is a good amount of suction and the carb butterfly plate. Could this sucking cause an initial resistance when pushing the gas pedal? Then once it is past its' initial position you wouldn't have as much suction on this area of the plate?

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post #2 of 4 Old 03-03-2013, 09:22 AM
slipjoint
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1981 CJ5 
 
Join Date: Dec 2012
Location: Marysville
Posts: 100
mine is like that till the engine warms up - then no issue.
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post #3 of 4 Old 03-03-2013, 10:39 AM
TIPPEDITOVER
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1978 CJ5 
 
Join Date: Jun 2011
Location: Puyallup
Posts: 2,047
There are some tiny holes in the bore of the carb just below and slightly above the butterfly plate. Some are idle fuel and some of them are transition holes from idle to part power. If any are clogged in can give flat spots just off idle. They are tiny and clog easy. Also a failed accelerator pump can cause your symptoms. How does the linkage on the carb feel with throttle disco'd? Some have a pretty good sized return spring. Maybe the accelerator pump linkage is binding or there is a problem there. Just throwing out some ideas for you.
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post #4 of 4 Old 03-03-2013, 10:46 AM Thread Starter
dnjeep
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1976 CJ5 
 
Join Date: Feb 2012
Posts: 98
Quote:
Originally Posted by slipjoint View Post
mine is like that till the engine warms up - then no issue.
I do know that it's way more previlent before warming up, but I think it's still there when warm (at least I think so, I can't recall for sure). I'll have to pay attention to that as I look into this more deeply.
After warm, does yours have any hesitation when going down the road (when you barely press the pedal keeping constant pressure at that first pressing)?
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