Sotck 71 240z carb problem

[woytovich]

With the air cleaner off am I likely to be able to see if the butterflies are sticking?

[Gary in NJ]

With the air cleaner off am I likely to be able to see if the butterflies are sticking?

No, but you will get a better view of the linkage. If the carbs were "messy", there is a good chance that the carb throat has a coating of carbon. Raise the suction piston so you can look inside (through) the venturi to the butterfly (it's really called a throttle valve). You might see a black coating in that area. A good cleaning with carb cleaner and a rag will get you moving smooth again. If the area in the throttle valve is coated, chances are the piston and chamber cover are coated too.

[woytovich]

The insides of thed carbs were cleaned completely when the werfe off... but I'll take a look again...

[5thhorsemann]

lets not forget from wence we came, a stall then high rpm. I'm gonna stick with the links

[woytovich]

lets not forget from wence we came, a stall then high rpm. I'm gonna stick with the links

There was no stall... very nice idle... theN when trying to press the accelerator very gently, as when pulling away from a stop in a senior citizen sorta way, I get nothing...nothing as I add pressure to the pedal (or linkage between the carbs with the linkage back towards the pedal disconnected)... then I get ZOOM... sudden RPMs.. There doesn't seem to be any "room" for the low fuel delivery needed for those low, off idle, RPMs. This problem shows itself between gears too if I let the RPMs drop while the clutch is in (while shifting)

[5thhorsemann]

can you feel the binding at the peddal or does it feel smooth?

[Mikes Z car]

My 71 did the sudden takeoff off from idle. I had cleaned the linkage and didn't get improvement not that that would never work I imagine. In later years I wondered if the throttle butterflies had dragged on the inside, on the side of the carb but that car was only 5 years old back then and I wouldn't think it would have done that at that mileage point. My current 70 240Z doesn't seem to do that for some reason and the linkage is still in the stock configuration as per Ron's posted link to a solution involving a modification. One thing I didn't do on my old car (as opposed to my "new" 40 year old car heh heh) is to take the "pivoting post" off and lube it.

Good job on your video Mark as it clarifies for me anyway the stuck aspect since you disconnected the gas pedal side of the linkage and show what happens with the engine running and you open the throttle by hand.

Mike

Edited November 27, 2010 by Mikes Z car

[Gary in NJ]

Mark,

I had the same problem you describe in post 17. I cleaned (removed and polished the inside of the plastic and the ball with a Scotchbrite pad), lubed (white lithium grease) & adjusted the throttle rods. The rod from the bell-crank to torsion rod was on spec (7-3/16") but the rod from the pedal to the bell-crank was long. It was readjusted to spec at 4-1/4". This mostly cured the problem.

Believe it or not, the final thing that made the on-throttle transition much smoother was a clutch adjustment. My clutch was engaging too high and when I lowered the engagement point the high break-out force of the throttle wasn't as noticeable.

[tlorber]

Sorry, I was unable to view your video. However, I went through a similar situation with my car, where there there was a sudden "jerk" upon acceleration.

Any point at which you can increase the radius of the "driving" member, and decrase the radius of the "driven" member will assist in smoothing out the transition. I believe there are at least 3 adjustments in the system where I bent the linkages to accomplish this. I even took off the accelerator pedal and bent the heavy rod beneath it so that my foot would contact the pedal further down. All of these together really helped the problem that I was having. I also rebushed the linkage that is attached to the firewall.

[woytovich]

Ok... so I spent an hour or so playing with this throttle problem and... no joy.

I disconnected the linkages close to the carbs and verified that they, and all of the linkages from the gas pedal to the carbs, move freely and are lubricated.

I pulled off the air cleaner and sprayed some carb cleaner up into the carbs (after raising the dampener thingy out of the way) There was a good amount of black carbon on the inside of the air cleaner and in the throat of the carbs.

I shot 4 more (smaller this time) videos... they are .mov files so you might need QuickTime to view them? - sorry...

http://www.woytovich.com/transfer/z

the new videos are carb3, 4, 5 & 6

#6 shows the choke being pulled... no problem there.... it does something different when sending fuel to the carbs... a clue maybe?

#5 asks about maybe some vacuum issue

#4 is just showing the dampener moving

Mark

Edited November 29, 2010 by woytovich

[Gary in NJ]

I don't know Mark, everything seems to be working real well.

Are you new to 240Z's? I've never owned or have driven a 240Z that didn't have a high break-out force on the throttle. When they get gummed-up out or of tolerance the car is almost undrivable. When they are sorted out they are stiff but you can develop a feel for the correct touch in a day or two of driving.

From what I see in your videos, your carbs are functioning well.

[woytovich]

This is my 1st Z... it IS difficult to drive comfortably as-is...