My 73 240z 'surges'...

[Dr_rich]

I am a new 240z owner and new to this forum. I have had my z for almost a month, and love my Z! But, when I am in first or second gear, I have to let the clutch out slowly and carefully or the car will 'surge'. Not engine revving, but it is like stabbing the brakes when you are driving. the only way to stop it when it is doing this is to either accelerate out of it or push in the clutch. I found and replaced the driver's side halfshaft u joints (having found one u joint bad- replaced both on that side). I am very perplexed as to what is causing this.

I am new to Z's, but I feel I have a pretty good understanding of the mechanics of the drivetrain. Some info that might be helpful is that the previous owner put in a 5-speed, but I have been underneath the car and have found no loose or missing bolts. One other thing is that I do get that familiar 'clunk' sound in the rear of the car when I let out the clutch.

Any help would be greatly appreciated. I have read many posts on this site and I am impressed by the vast knowledge therein.

Thanks!

~Richard

[beandip]

We really need more information. Is the engine equiped with round top SUs or the flat tops ? What ignition is installed , stock with points ? Are you speaking of the ''surging '' when the engine is other than normal temp. ? The clunking is for another thread . Lets concentrate on one thing at a time.

[EScanlon]

Before you go crazy disassembling and "fixing" things, would you do one simple easy test?

Get in the car, and in a nice level area, let the clutch out slowly, but DO NOT ACCELERATE. In fact, take your foot completely off the accelerator pedal. I have a feeling that your "surge" will disappear. If so, you can repeat the test going to 2nd gear the same way, shift with no accelerator. If no sure, it's your foot and not the car. (Well, ok, technically it's the car.)

If it does, then what you are suffering from is the dreaded Accelerator Pedal Surge. This is due to the geometry of the accelerator linkage. There are cures for it, but I haven't heard of any easy ones.

The best thing to do, is do what most of us have done, learn to work with it.

Enrique

[Dr_rich]

Here's some more info: I have round top SU's and 280zx electronic ignition, But the engine isn't surging. I wish I could describe it better. I have had the car on level ground and let out the clutch and it's fine. I do notice it is more apt to happen at higher rpms.

Could a worn front differential mount cause this? or maybe loose differential internals?

When I had the rear of the car on blocks, I manually turned the rear driver-side hub forwards, and the pass side wheel turned the opposite. I know that is normal, but I also noticed there was a little play when I turned the rear driver-side hub before the pass side turned. Not much, but a little. Is that important?

As far as the linkage goes, it's all brand new. The carburetors were completely gone through and new linkage installed before I bought the car. But again, the engine doesn't change rpm at all, it has to do with something from the transmission rearward...

~Richard