I'm in the process of making my 72 240z road worthy, and it's just about ready. However, when i try to accelerate quickly the car studders for a sec, then accelerates fairly smooth. The car will rev up easily and smoothly when in neutral, and driving it around makes the problem a little bit better. I'm kinda stumped on why it accelerates in gear the way it does. So far I have:

-rebuilt ALL the fuel system

-put new plugs and points

-new thermostat

-new fluids

-Dialed in the carbs and cleaned them up

That's all I can remember right now that could effect the acceleration, any help to solve this would be greatly appreciated!

Chase

Do you have oil in the carb dampers?. Silly question, but you never know.

Does running with the chokes part on help at all.?

Yes, the carb dampers have fresh oil in them. I have not driven the car with the choke on, it idles higher as usual and accelerates fine in neutral with it's engage.

Have you checked your timing?

If your car runs better with the choke on a little, it would suggest to me it is running a bit lean, and that could be your problem.

Richen each carb quater turn and see how she runs.

Yes, the engine will run faster at idle with the choke on.

Edited October 26, 201113 yr by olzed

Perfect timing for this thread. I'm having the exact same problem. Runs better with the choke at about 3/4 and starts to break up around 4500 rpm.

Have you checked your timing?

Yes, I've put brand new points and have them set to .021 according to the Haynes manual. Should I open them up more?

Have you checked your timing?

Yes, I've put brand new points and have them set to .021 according to the Haynes manual. Should I open them up more?

That's not the answer to the question he asked. Is your distributor set at roughly 17° @ 650~700 rpm? (IIRC, that's the setting for a 240Z - I had a 280Z most recently which would be different)

That's not the answer to the question he asked. Is your distributor set at roughly 17° @ 650~700 rpm? (IIRC, that's the setting for a 240Z - I had a 280Z most recently which would be different)

Sorry about that, yes the distributor is set at proper timing.

What oil are you using, 20w?

Have you verified your vacuum line is attached and working properly; put your light on and check to see how it advances with and without the line plugged in.

Edited October 26, 201113 yr by Healey Z

I see that you didn't mention anything about the plug wires, have they been recently changed?

You said it runs better after being warmed up-right? That would indicate a mixture problem.

It is hard to compare engine conditions when just revving up motor in neutral compared to while engine is under load.

Bad Ignition wires will act fine in the garage revving the engine, but under load the engine will studder.

Same as a mixture issue, under load the engine acts completely different and it's requirements are different . Mixture might just be good enough, or there is just enough fuel in the float bowls for revving in the garage, but insufficient under loading.

Thanks guys for all the input! Healey, I can not remember what oil I used off the top of my head, whatever the service maunal recommends. How easy is it for the advance to move? Pulling the line off and running it doesn't do very much, which probably indicates a poorly working advance. I have a hard time even moving it by hand.

Madkaw, the plug wires on it are the same green NGK wires that came with the car when I got it. Putting new ones on the car is a good idea since I don't know how old they are. If I let the car warm up in neutral, then take off to drive it, it runs great till I accelerate fairly quickly. It feels almost like I surprised the car or something.

My plans are to check the timing, ponts, and check the mixtures. I'm fairly certian it has someting to do with the timing. If the problem is still there then I'll get a new set of plugs and possibly a vaccum advance.

Chase