Sotck 71 240z carb problem

[woytovich]

Take a look at the video below. I am experiencing a problem with the linkages or carb setting on my 71 240z with original carbs. The symptom is that when stepping on the pedal (or pushing the linkage by hand) there is some resistance just before the linkage starts to move and then it "surges" so that I go from idle to higher RPMs rather than being able to gradually increase RPMs... this does not APPEAR to be binding in the linkages... but I can't be sure.

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

sorry for the large videos... I'll repost them smaller later...

Any thoughts?

Mark

Edited November 26, 2010 by woytovich

[5thhorsemann]

Dirty linkaces that are binding. My car did the same thing, disassemble clean lube and reassemble. First, take the peddal apart from the motor portion to see which end is sticking.

[Gary in NJ]

Every junction of that linkage should be sprayed with white lithium grease annually; starting at the pivot point on the accelerator right on down (up?) the line. Also, the FSM provides the proper length for each section of the linkage. If its never been checked it's worth measuring and adjusting. One wrong section can make for sticky/abrupt throttle operation.

I also agree with Mr. Horsemann that a good cleaning will go a long way to reduce the high break-out force required to get your butterfly valves open.

[geezer]

Here is a link to the Z Car Home Page that illustrates the problem and a cure. This simple modification may be helpful.

http://zhome.com/

- Scroll down to - Z Technical Library

- Click on - Index of Technical Articles

- Scroll down to Intake System

- Click on Improving the Throttle Linkage or Getting Rid of the Jerk! in your early Z car.

Edited November 26, 2010 by geezer

[SteveJ]

Here's the link to the article Ron is talking about.

[woytovich]

Thanks for the info and I will take a look at this once I'm back to the car on Sunday... but I'm thinking it is something else. If you look at the video you'll see that it happens even with the linkages back towards the firewall disconnected...

...but wait... are you saying that the behavior of the carbs and their throttle levers is corfrect and that the problem is that the movement of the linkages can be adjusted to make their movement through the first 1/2 inch slower... therefore making off idle acceleration smoother?

[5thhorsemann]

You can't adjust the ratio between pedal and butterflies through the linkage, there is however adjustment is many of the linkage components to adjust out binding and component interferience issues. I would shoot for a good clean and lube before you talk yourself into biger troubles, it's a quick job if you don't find things needing replacement.

[woytovich]

You can't adjust the ratio between pedal and butterflies through the linkage, there is however adjustment is many of the linkage components to adjust out binding and component interferience issues. I would shoot for a good clean and lube before you talk yourself into biger troubles, it's a quick job if you don't find things needing replacement.

Well the linked article does do that, adjust the ratio (well at least the force required to make that first little movement)

I have lubed it all (and it was all apart when I pulled the carbs to clean out 25 years of thick old fuel) There is no APPARENT binding when moving the parts individually by hand... but i WILL revisit all of that.

Another thought... could there be a problem with the needle (bent/friction) and/or dampening (sp) oil (too thin) in the carbs?

Mark

[Gary in NJ]

Another thought... could there be a problem with the needle (bent/friction) and/or dampening (sp) oil (too thin) in the carbs?

There is no direct link between the throttle linkage and the needle or the bell housing. These are Constant Velocity carbs. Changing the oil will have no effect on the break-out force of the throttle.

Something is binding. Work the problem.

[woytovich]

There is no direct link between the throttle linkage and the needle or the bell housing. These are Constant Velocity carbs. Changing the oil will have no effect on the break-out force of the throttle.

Something is binding. Work the problem.

I understand that there is no direct link... I thought that IF the needle was sticking it would take longer for it to move...

Thanks... I'll keep watching here for any other insights but I'll be a cleaning and lubing fool on Sunday! THANK YOU

[5thhorsemann]

The butterfly may be sticking in the throat, the needles are vaccume acuated, the damper likewise shows problems under vaccume, not a related issue.

Back to the butterfly, this is one of the bigger problems I was refering to. I didnt realize you already did the clean and lube process, But the binding may still be in the linkage. Pull the Air filter and anything else that obstructs clear view of the linkage and give it a complete visual inspection, then pull off the returne springs and actuate the linkage by hand, GENTLEY. You may find that without spring pressure the off throtle bind goes away. If you can't find the trouble outside the carbs in the linkages, butterflies are all that remain. The needles jets piston and dampers sound to be okay if you get an even ramp up to high RPM.

[5thhorsemann]

Remember there are 2 sets of CV needles and both are unlikley to fail at the same time, one fails and you get a funky off throttle RPM ramp.