Weird Engine Acceleration Issue
 

Hi,

I'm new here. I own a '79 datsun 280zx. Lately I've noticed that there's an acceleration issue with the car. When I drive the car, there's a lag between the RPM/tachometer. It's a stick shift. When I'm driving, and shift into neutral, I hear that the engine is still accelerated and that the tachometer is still reading the RPM at which i was running. But after about three seconds when the car stops, the RPM drops down... It's like a delayed response. Can someone please help me resolve the issue? when the car is stationary, idling.. it has no problem at all.. only when driving

Thanks

Welcome to ZDriver! :006:

Let's start with the basics...

When was the last major tune up / check over done?
If you haven't bought a Haynes manual or downloaded the FSM, I suggest doing so now.

www.xenons130.com/reference

Hi

thanks for responding. The car passed emissions and inspection 3 days ago. I recently changed spark plugs and changed the engine oil.. battery, and alternator. The engine starts every time and sounds great. When I rev up the car in neutral the tachometer responds normal and the revs from the engine are normal... Its only when I'm driving is that the RPM's seem to be sticking when I shift the car in neutral. When I come to a complete stop, you can hear the enginee still accelerated and the tachometer still showing about 1500-2000 rpm.. but after 2 or 3 seconds it the tach falls back to normal and so does the engine revs back to normal. I've also noticed that the speedometer needle shakes a little... It's been a real head scratcher figuring what's wrong

I disconnected the cruise control thinking it may be that and I also started to inspect some of the rubber hoses on the engine but no luck

Sounds like something is sticking - the only way to accellerate is to let more air in. It sounds like the throttle body is sticking open. That would be the linkage, a return spring or the throttle plate itself is sticking.

I checked the linkage and the return spring today but it seems fine.. Some cables were torn at the end, which I fixed but the problem still persists. It's only when Im driving and I shift into neutral such as stopping for a red light or going down a hill. If I rev it standing still, everything is normal.. do you think changing the PCV valve will have an effect?

haha my 79 does the same thing ive gone crazy tryna figure it out it l hang at about1500 for about 3 secs then go down wen i comlpetely stop idk what it is ive even gone to the point were i tow it with another truck while its on and as soon as i hit about 5 mph the rpm aautomatically go up on its own my car is possesed

yeah haha its a strange problem.. i may clean the throttle body sometime soon when I have free time.. but my last resort will be to change the intake manifold gasket

What do you think that's going to do?