Does carb supply fuel during deceleration?

[bushbean]

Howdy,

Just a simple question for carb experts: when decelerating with your foot off
the pedal and the transmission in gear, does the carburetor continue to
supply fuel into the intake manifold?

Thanks. Just trying to figure out why my ride is so jerky when my foot is
a bit rough with the throttle.

[FyreDaug]

Yeah because there is always vacuum pulling fuel into the cylinders, but think with your foot off, that means the throttle plate is closed right? What normally happens like that? It idle, so basically what its doing is supplying it with the amount of fuel required to idle just faster.

[MessyHonda]

well in my carbd car when i am going like 3000RPM@like 75mph and when i take my foot off it it goes down to like 2700RPM.....i guess that is how the automatic works. it keeps the car in gear until your speed drops alot.....i stay in high gear till about 40mph and then it downshifts....im not sure about how jerky the car after you let your foot off it.....on my lx-i with manual i hit the clutch and my motor goes to 750rpm......maybe you should replace the fuel filters.....when i did i felt a faster response...good luck

[A20A1]

With the throttle closed and rpm high, vacuum will spike to 30"+ so you'll be pulling fuel from the idle circuit mostly, probably more fuel then at idle which is only about 24" vacuum.

[bushbean]

well in my carbd car when i am going like 3000RPM@like 75mph and when i take my foot off it it goes down to like 2700RPM.....i guess that is how the automatic works. it keeps the car in gear until your speed drops alot.....i stay in high gear till about 40mph and then it downshifts....im not sure about how jerky the car after you let your foot off it.....on my lx-i with manual i hit the clutch and my motor goes to 750rpm......maybe you should replace the fuel filters.....when i did i felt a faster response...good luck

Actually, I am looking for a slower response when I lift my foot off the gas.
When I lift my foot, the car jerks back (not much but annoying). I want
to transition to go smoother, i.e. slower response. I've driven many cars,
but I've never experienced this jerk back except in my Accord. I know
the original owner very well, and he told me this Accord has behaved this
way since the day in rolled out of the dealership lot. I've seen the way
he drives; he press down on the clutch pedal to avoid the jerk. He thought
that was normal for a torquey engine. I didn't know Honda engines are known
for their high torque. He also told me that this Accord likes to eat clutch
and brake pads. The car is 200,000+ miles, and is on it's 3rd set of clutch.
Anyway, the jerk is very annoying and uncomfortable. For example, the jerk
is very harsh if I was doing 25mph at 3rd gear and suddenly lift my foot
off the gas pedal without pressing down on the clutch at the same time.
The original owner thinks it's normal. Do you guys think this is normal? Should
I have a carburetor expert look at this?

[ChaseR]

3 clutches 200,000 miles sounds about right actually....

[FyreDaug]

With the throttle closed and rpm high, vacuum will spike to 30"+ so you'll be pulling fuel from the idle circuit mostly, probably more fuel then at idle which is only about 24" vacuum.

Right. yeah with the higher rpms and the closed throttle you will have higher vacuum, and that vacuum is used to pull the fuel from the carb. I wonder what happens when you turn the car off in gear. It slows down more, obviously its not firing, maybe that uses less fuel? Itll be dumping it through the exhaust though. Dont suggest doing it anyways :p:p

[ChaseR]

Yeah I have accidently shut my Car off while driving, I always thought it was just turning the crank and burning excess fuel...

[FyreDaug]

Yeah I have accidently shut my Car off while driving, I always thought it was just turning the crank and burning excess fuel...

well isntead of the engine turning the trans, the trans (being driven by the axles) turn the engine. Doesnt do any harm, its just if its carbed its suckin the fuel outta the float and dumping it in the exhaust

[2oodoor]

well isntead of the engine turning the trans, the trans (being driven by the axles) turn the engine. Doesnt do any harm, its just if its carbed its suckin the fuel outta the float and dumping it in the exhaust
I dont neccessarily agree with that , the only way fuel goes into cyl when decellerating is if the throttle plates are open. Normally that condition does not exist with any make of car. /there may be a long term problem or adjustment going on with this car. these carbs do hold the throttle open with throttle controller when your not even touching the gas, but there are controls that moderate the opening until the reason is accomplished, A20A1 , what do you think , well he knows these carbs inside and backwards. Normal model cars do have what is called a dashpot that when you decel, you dont get the gas flow and backfiring . but Honda has its own unique way of dashpotting on the kelken carbs. Also there is a fuel cuttoff solenoid that cuts of fuel flow from float bowl at certin times.
Also three clutches in i200K miles could be kinda excessive, but its hard to say if oem parts were used , condition of flywheel etc. that would determine that kind of stuff. Myself when decelling from highway speed, just put it in fourth till it starts to jerka little and then put it in neutral until its tiime to go again, then use appropriate gear.p\ other things to check to adrdress your specific complaint leaving the carburator outta the conversation would be motor or transmission mounts, pressure plate-there bad about being reused on clutch jobs, and ignition timiing.

[carotman]

It could come from the engine mounts too. Check if they are worn or damaged.

[FyreDaug]

I dont neccessarily agree with that , the only way fuel goes into cyl when decellerating is if the throttle plates are open. Normally that condition does not exist with any make of car. /there may be a long term problem or adjustment going on with this car. these carbs do hold the throttle open with throttle controller when your not even touching the gas, but there are controls that moderate the opening until the reason is accomplished, A20A1 , what do you think , well he knows these carbs inside and backwards. Normal model cars do have what is called a dashpot that when you decel, you dont get the gas flow and backfiring . but Honda has its own unique way of dashpotting on the kelken carbs. Also there is a fuel cuttoff solenoid that cuts of fuel flow from float bowl at certin times.
Also three clutches in i200K miles could be kinda excessive, but its hard to say if oem parts were used , condition of flywheel etc. that would determine that kind of stuff. Myself when decelling from highway speed, just put it in fourth till it starts to jerka little and then put it in neutral until its tiime to go again, then use appropriate gear.p\ other things to check to adrdress your specific complaint leaving the carburator outta the conversation would be motor or transmission mounts, pressure plate-there bad about being reused on clutch jobs, and ignition timiing.

Which part dont you agree with? It sucking the fuel from the carb when the car is shut off in gear? Im sure it would be getting some fuel, that vacuum coming through the intake manifold has to go through the carb, and carb vacuum is what supplies fuel from venturi right?

[2oodoor]

yeah Frye, I will stand by my thoughts about the throttle controller, and I agree with A20A1 about the idle circuit , but that would not be 'dumping' gas into the cyl.. I used to have a volare with manual trans, that had hollowed out converter and I could floor the gas just at the same time cut the key off, then cut the key back on, and POW like a M cocktail. gas was going thru cyl to exhaust unburned, then when I cut the fire back on it ignited in the exhaust system.