I have a 1990 300zx n/a that has a bad hesitation when accelerating every time i take off from a stop and when i shift gears when i press the gass it just falls on it face and then goes. Also after i drive it and shut it off its really hard to start back i have to hold the gas pedal down for it to start. Ive replaced the tps,maf,spark plugs with ngk plugs nothing seems to help also the idle jumps around one minute its idleing around 700 next it around 1500.any help would be appreciated.

Consider looking at all the sensor connections for corrosion and clean. Possibly pay attention to the engine coolant temp sensor with the two wires, since you are having hot start issues. I had a similar random idle bouncing and replaced/swapped just about every sensor, in the end oxygen sensors fixed the problem.

itsa300zx wrote: ↑

Sun Jan 20, 2019 10:30 am

Consider looking at all the sensor connections for corrosion and clean. Possibly pay attention to the engine coolant temp sensor with the two wires, since you are having hot start issues. I had a similar random idle bouncing and replaced/swapped just about every sensor, in the end oxygen sensors fixed the problem.

Agreed, especially since the O2's can also become intermittent with age. The Z32 unfortunately suffers from corrosion more than many other vehicles and how bad things are can affect a number of areas so consider fixing/replacing any corroded connectors and/or harnesses you find, and also check all vacuum lines for best long term results.

Ok ill look at the connectors. I did find some vacuum leaks and since i fixed them the idle has been better it stays around 800 or 900 but im still haveing the hesitation and hard to start after driven

I checked the codes on the ecu and only code i got was 34

Code 34 is the Knock sensor, most likely a bad sub harness and/or connector, should not affect a hot start issue. Have you checked/tested the ECU coolant temp sensor? Here is what you should expect in terms of resistance readings :

2.1 to 2.9 kOhm @ 68F ie cold engine at room temp
0.68 to 1.0 kOhm @ 122F
0.30 to 0.33 KOhm @ 176F ie fully warmed up engine.