Weird Throttle

[stripperpole]

Hey all, new to the forum.

I have a stock '74 CJ5 AMC 258 i6 / 4.2l /T-18 /Dana 20 . The issue I'm having is the throttle seems to "tight" I guess. When you put your foot on it, it's either 800rpm or 4k. Just replaced the throttle cable today, even though the old one really didn't show any signs of wear. The Jeep belonged to my dad before he passed and he said that it'd always been that way. I'm wondering if it's a carb issue? Or if anyone's ran into this before?

It sat for several years, just pulled the tranny to put a new clutch kit in it because the throwout bearing was making a ton of noise. Would like to get this issue put to bed, because it makes it pretty difficult to get going smoothly. Any advice would be appreciated.

Edit to add: I've done a full tune-up within the last two weeks. And although it's been sitting for quite some time I'd always just start it and let it run once a month or so. I sprayed some Chemtool carb cleaner in it but haven't actually taken the carb apart yet.

 

[mtnwhlr]

I would be looking at the return spring on the carb.

 

[stripperpole]

I would be looking at the return spring on the carb.

I should've mentioned it in the thread, but the spring looks mostly new. And besides that even with the spring off it still feels the same way. When you start pushing the pedal in, it almost feels like it's getting sucked to the floor.

 

[Scout1067]

I would be looking at the return spring on the carb.

I would say check the Throttle Return Spring first as well. The stiffer the spring the tighter and harder to push down your gas pedal will be.

 

[Lumpy Grits]

Sounds more like mechanical interference like binding throttle shaft etc.
Time for a full rebuild.
Does the floor pedal move freely?
LG

 

[cglax6]

Sounds more like mechanical interference like binding throttle shaft etc.
Time for a full rebuild.
Does the floor pedal move freely?
LG

LG hit it on the head...

Looking like a full rebuild is in your future. I've owned boats and cars with carbs and can't tell you how many issues I've had just disappear after taking everything apart, give a thorough cleaning, and put back together. By no means am I a master mechanic, but this is the route I'd go.

 

[stripperpole]

Sounds more like mechanical interference like binding throttle shaft etc.
Time for a full rebuild.
Does the floor pedal move freely?
LG

Yup that's kind of what I figured. I ordered a rebuild kit from summit late last night, hopefully that'll fix my issue. The pedal moves fine, when disconnected from the carb it's smooth as butter. I was also wondering if it could be the coiled spring on the throttle shaft closer to the carb. It's a bit rusty. Thanks for the help.

 

[mriplaybass]

If the pedal moves freely when disconnected from the carb, disconnect everything from the carburetor, throttle cable, return spring, manual choke, if you have one. Then try to operate the throttle by hand. I am guessing that it will still be stiff. I would look at the throttle plate shaft. With the carb removed, work the throttle plate back and forth while applying something like PB Blaster, WD40, or some other product capable of cutting through any built up varnish and corrosion to the shaft from inside and outside the shaft bore.

 

[stripperpole]

If the pedal moves freely when disconnected from the carb, disconnect everything from the carburetor, throttle cable, return spring, manual choke, if you have one. Then try to operate the throttle by hand. I am guessing that it will still be stiff. I would look at the throttle plate shaft. With the carb removed, work the throttle plate back and forth while applying something like PB Blaster, WD40, or some other product capable of cutting through any built up varnish and corrosion to the shaft from inside and outside the shaft bore.

Yes it's still stiff. Another thing I should've mentioned, when operating the throttle by hand, revving up goes fine. But when coming back down, there's a noticeable "click" or like a jump, where it feels like it's binding on its way back down. Just one spot, maybe a quarter of the way into the throttle. You'll rev it up, then as you let it back out it'll go smooth, hit that spot, then continue smoothly until idle.

 

[mriplaybass]

Sounds like you have some corrosion or varnish built up in there. Try the lubrication I suggested before. If the throttle plate shaft is severely corroded, you may just have to replace it, or you will have a vacuum leak around the shaft. Or, just get a different carb.