# 1986 300zx



## rememberrev7 (Mar 4, 2015)

I've had this car for about a year now and it's had a problem with the fuel system from time to time. It feels as though the fuel gets cut off for a sec and then restored, kinda makes the car buck back and forth. I'd put fuel system cleaner and it would fix it for a few months. But for the last week it's been bucking and hesitating when I drive. It's also been shooting black smoke and idling high (around 1,400 rpm). I recently switched out the ignition wires for NGK because Bosch ones wouldn't fit correctly and it would throw spark from the cap and rotor. Was wondering if anybody had any ideas or experienced something similar?


----------



## smj999smj (Jan 1, 2006)

Black smoke is an indication of unburned fuel. I would check the vacuum hose to the fuel pressure regulator, first, and then check the fuel pressure to make sure the regulator is working properly and fuel pressure is up to spec. That "cutting out" or "bucking" could also be the result of a bad distributor, which isn't uncommon on VG engines.


----------



## rememberrev7 (Mar 4, 2015)

Yeah, I thought it could be a vacuum leak as well. But I'll check everything else you mentioned and let you know if it is one of those things. Thank you!


----------



## rememberrev7 (Mar 4, 2015)

smj999smj said:


> Black smoke is an indication of unburned fuel. I would check the vacuum hose to the fuel pressure regulator, first, and then check the fuel pressure to make sure the regulator is working properly and fuel pressure is up to spec. That "cutting out" or "bucking" could also be the result of a bad distributor, which isn't uncommon on VG engines.


Turned out to be a bad fuel injector as well as a throttle body position sensor. Thanks for the advice anyway though!


----------

