Thread: wont rev after warm up

i have a 94 sentra se-r with the uk primera 10:1 compression engine swap.
i picked up this car with this issue i figured it would be an easy fix but its kicking my ass. The car runs great until it gets to opperating temp which i think is putting it into closed loop. when this happens at full throttle the engine will not rev up but if i give it 1/4 throttle it will rev up. i have ohmed the tps tested the maf replaced dizzy, cap, rotor, iacv, and temp sensor. i tried unplugging the o2 when it did this no change. i even swapped the ecu with no luck. the ecu flashes a 34 code which i think is a knock sensor code i unplugged that and tested the sensor no problems there. i tested the coil and it works great. To me it cant be mechanical because it is only happening when it goes into closed loop. i found what i think is the egr temp sensor in the spare parts that came with the car but i dooubt that is my issue. i dont have a gauge to check fuel pressure but i doubt that is my issue as well. i need some suggestions

Idk if it the same but my buddy Civic had the same problem, 1/4 throttle and it will hit Redline, but when you WOT it would choke. Got a new fuel filter and the line had some stuff in it which wasnt let enough fuel to come when WOT.

i hookep up a fuel gauge today and it seemed normal till the problem started happening and the gauge started flickering back and forth real fast around 40 psi i unplugged the regulator and it just did the same thing at 50 psi. i swapped the relay no change. so i took the fuel pump out and it was origianal. so i will start by replacing that and the fuel filter.

Get a 300zx fuel filter

It sounds like you haven't rule out a bad O2 sensor yet. You said you unplugged it and there was no change. Sounds like it might be bad then?

My other suggestion was to check the ECU's water temp sensor (not the dash one) but you say you've replaced it? You sure the wiring is good for it?

check the harness first. if it flashes a 34 code, possible sensor problem or wiring problem. check for connectivity from pin 27 of the ECU up to the connector of the knock sensor.

I'm a little late to the party, but my G20 is doing the exact same thing. I get hesitation under load only in closed loop. Backing out of the throttle helps the car accelerate. The ECU throws code 34.

The car has recently had a new fuel pump, grounded 4-wire Bosch O2, plugs, wires, cap, and rotor. I also tried good working MAF and coil from my SE-R. TPS voltage and MAF ground also check out.

Ever find out the problem?

Whenever I get the time, I'm going to check the harness connection and swap in a spare knock sensor I have off a parts car.