engine bucking help

[Advan280z]

just got a 75 280z. it has been sitting for a few years. but it has been started etc to keep it not seized.

the car seems to have nice power..it idles perfectly at 800rpms, but during a certain point when driving it will hit a wall and you have to floor it to get passed the hurdle then it drives fine. any ideas? seems like also it hits at a certain rpm i think its in the 3k band.

any feedback?

thanks

~B

[JEFF]

Have you done anything in the way of tune-up items? Is the engine stock?

- Jeff

[Advan280z]

all stock.

[Fun_in_my_z]

Had that happen on a V8. Check your plug wires,your carbs, and your timing.

I ajusted the timeing that helped some. Rebuilt the carberator that helped to.

But it wasnt gone totaly. I started going throught different things checking them, and for the heck of it checked the plugs and wires. Found two that where messed up. Changed them and problem solved. :classic:

Good luck Bill

[240ZX]

In addition to the above mentioned items you may consider syncronizing the SUs. You may also have some old fuel and or water in the tank.

[ChrisA]

In addition to the above mentioned items you may consider syncronizing the SUs. You may also have some old fuel and or water in the tank.

Ummm...unless he's converted to SU's I would think he's got fuel injection. Not nit-picking or anything. Just dont want to confuse him with terminology he doesnt know about.

:laugh:

Chris

[240ZX]

Thanks for the correction Chris....no harm, no foul !!!

[AxtellZ]

I'll say right upfront, i know bumpkus about FI, but i would also check out the possibility that its AFM related. Could be a temp sensor, again not sure the FI system...

Has it had a complete tune-up, so we are working with known good condition basics?

[Robin]

Sounds like the throttle valve switch, (located on the throttle body). If they get wet, or bad continuity from whatever you will not be able to go above 3000 rpm. Disconnect the wire lead going to TVS.... clean and dry out the connection. good luck

[sblake01]

The TVS also needs to be adjusted correctly and the contacts inside of it need to be clean. I believe that this is covered in the FSM

[Advan280z]

you wont confuse me, im not a newbie in the car world. it is efi though

i have extensive experience in rotaries (87 rx7 turbo) that ive done everything with pretty much.

the car had been sitting for a long time, i just bought it. i put in injector cleaner, filled it up with super, changed the oil/filter. plug wires look pretty new. but, not sure on the plugs.

it will go past 3k, it just shudders, and i just step on the gas and it goes through it and power is back to normal. sounds like ignition (i hope)