hesitation w/ fast idle cam step

[brian_wildcard]

hi all, it's been a while since i posted
i had a good summer driving my car around despite those gas prices

as the weather's getting colder i'm starting to get those hesitations back in last winter.
I've narrowed it down to a lean-hesitation (sometimes stalling) when accelerating with engine cold
and only happens when the fast idle cam on the carb is stepping down to the next step
almost like the moment the choke plate opens up that extra bit,
the carb is letting too much air in and causing a stumble
there is no hesitation when cam is not stepping down / when engine is hot

just to clarify my choke breaker isn't functioning,
but i've replaced it's function by adding a paper clip to the mouth of the carb, to hold the choke slightly open

my guess: is my fast idle cam out of sync? how can this be adjusted?

thanks again

[splatterdog]

With the breaker bad/disabled and only a paper clip to hold it open , it's your choke plate that's out of sync. The cam only does what the spring tells it to.

Fix carb or better a weber! Don't forget to do the mandatory vacuum leak check on all the old plumbing.

[brian_wildcard]

whoops, i just realized i started the thread in the wrong section, my bad

anyhow, it was by doing the vacuum leak check that I found out that the choke breaker was bad
if the choke plate was out of sync, why would I only feel hesitation the moment the cam is stepping down?
there is no stumble any other time during cold engine operation
(I could tell it was during the cam step down process, as after each hesitation the engine rpm would drop to the next fast idle level)

according to my research, the choke breaker's operation is to pull choke plate open when engine first starts (the reason I use the paper clip)
as the engine warms up, i can drop the fast idle cam to the next level by blipping the throttle, and this process does not require the choke breaker

i'm guessing then, that the problem therefore lies in why the there isn't a smooth acceleration when the cam steps down (when i blip the throttle)
what are your thoughts on this

[splatterdog]

Maybe too much choke? To get the cam to step down, you have to give it some gas. Accelerator pump squirt on top of a too rich choke could be causing your stumble.

The FSM doesn't have a spec for how far it should be open with the breaker applied to the choke plate. But if you look at the checking procedure, the SST shown in the manual looks a bit bigger than a paper clip. Maybe if someone here has an aftermarket carb kit instructions lying around. That may have a spec listed. Drill bit is the most common measuring tool for checking pull-off.

Wether or not this is in fact your problem, I would not look over a known bad part that happens to be part of your carb circuit that is there for warm up driveability.

Maybe try a thicker choke breaker bypass wire for fun.

[takza]

I can tell you that after installing a manual choke...that the 3AC with the OEM carb is very sensitive to choke position. My old autochoke worked real well...but I occasionally needed to use some carb cleaner on the shafts and then some light oil to keep it moving smoothly.

[brian_wildcard]

thanks for the reply guys
and thx to admin for relocating the thread

um, i've been doing some thinking
trying to break down the procedure on how the fast idle cam steps down

so first the spring in the electric housing is heated up by the current and begins to turn
when i blip the throttle, which part will move first?
1) the choke plate?
2) the fast idle cam?
or they move together?

if the choke plate moves first, then the fast idle cam will still be in the previous step
==> lean hesitation?

if the fast idle cam moves first, then the choke plate will still be closed
==> rich stumble?

i'm trying to keep in mind that the AAP diaphragm will be giving an extra shot of fuel everytime i accelerate

[brian_wildcard]

yes i am in the process of finding a part that can be mounted to the mouth of the carb
that is also the thickness of a drill bit

Maybe too much choke? To get the cam to step down, you have to give it some gas. Accelerator pump squirt on top of a too rich choke could be causing your stumble.

The FSM doesn't have a spec for how far it should be open with the breaker applied to the choke plate. But if you look at the checking procedure, the SST shown in the manual looks a bit bigger than a paper clip. Maybe if someone here has an aftermarket carb kit instructions lying around. That may have a spec listed. Drill bit is the most common measuring tool for checking pull-off.

Wether or not this is in fact your problem, I would not look over a known bad part that happens to be part of your carb circuit that is there for warm up driveability.

Maybe try a thicker choke breaker bypass wire for fun.

[brian_wildcard]

ok.. more thinking

when there is hesitation, stepping harder on the pedal would stall the car
(this has happened when i am trying to make quick left hand turns in traffic)
it FEELs like a lean stall to me

however, AAP diaphragm should be giving extra shot of fuel...
which is what i don't quite understand

[takza]

Vacuum leak....that the draw from the brake booster adds to?? Sometimes a shot of WD40 into the place the vac hose goes on a booster will eventually free up that valve in there?

[brian_wildcard]

o... should have said things more clearly
i was actually referring to the gas pedal, not the brakes

Vacuum leak....that the draw from the brake booster adds to?? Sometimes a shot of WD40 into the place the vac hose goes on a booster will eventually free up that valve in there?