HELP very bad 240sx problem

[sohcistehsex]

Hi, I am an auto student and I have an 89 hatch and a totaled 91 coupe parts car.

I swapped the motor from the 91 into the 89 and I wired everything correctly at the dash and swapped ecu and wiring harness.

the motor ran well in the 91 but after it was totaled(not my fault btw) it sat for a few months before i put it into the 89

I am having a bad problem with acceleration and starting and idling with everything hooked up correctly.I checked fuel pressure using a t-gauge at the fuel filter i got plenty of fuel pressure(34-44 psi)car stumbles and wants to die between 1k-2k rpms with mafs pluged in and vaccum hose going to FPR connected

when i disconnect FPR vacuum line and pump gas pedal to wot each time i pump it the rpms go up about 1k or 2k then it falls on its face until i let gas pedal up and pump it againbut if i keep pumping the gas pedal it will rev out

If i take the mafs plug off the car will idle and drive 100% fine but it bogs at 2600rpm like it hits a rev limiter(fail safe mode)

why would the car run fine in fail safe mode but super crappy with mafs connected in regular mode unless mafs is bad

I pulled the codes from the ecu after plugging mafs in and reseting ecu codes then starting the cari get 55 all clear it was my impression that if a mafs is bad it will throw an ecu code 12 and it will not go over 2600 rpmsthe ecu is saying all clear and if the mafs is connected it will rev out if i pump the gas fast so i thought the mafs is good but when i disconnect the plug it runs and drives fine(except not revving out past 2600 and the ecu throws code 12(mafs) like it should

if it is a problem with fuel pressure it should still run crappy when the car is in fail safe mode(mafs disconnected) shouldn't it?

so if a mafs on a dohc is bad will it cause the car to run like crap and if it is bad could the ecu still think it is ok and give a all clear code 55

also will a FPR do this and will a FPR from a SOHC work on a DOHC(looks the same but i dont know)

please guys help me out if you can, if you cant then thanks anyway but i am getting really frustrated by thisi dont want to go buy a mafs(200$-300$) or a FPR(130$) if thats not the problem i need it running within 3 days so i can get to school

[sohcistehsex]

Ok i got the car running pretty good now its still bogs a little now but its drivable and semi-idling

its my mafs pretty sure i took it off and unscrewed the two screws and sprayed CRC mass air flow sensor cleaner all through it(i used a whole can damn near and cleaned it twice) as soon as i was done i dried it out and put it on the car

it fired right up and held a solid idle at 750 and i drove it and it seemed perfect then like 5 minutes later it started bogging a little bit so i think my mass airflow sensor is still bad but the CRC mafs cleaner helped it 1000% and at least its drivable till i come up with 250-300 for a new one(next friday is a long ways away i wish i didnt spend damn near my whole paycheck on friday & saterday)

[martins_240sx]

hey thanks for the help on my car...Im gonna say your problems is your mass too. mine was bad and it didnt throw a code either. I got mine today for free, luckily, a little shop here does swaps and had one laying around. Your question about the fpr, if they were the same, Im gonna say yes cause both motors use the same fuel pump and use about the same flow and most nissan run at 34 and 44 psi anyway... if worst comes to worst just change them back, its only two screws.

try a junkyard for the mass