I have no idea what's going on with my 1990 nissan 300zx NA. I have another motor in it (motor has about 150,000 miles) and anything under 3k rpm it chugs like hell and almost stalls itself. And dont even think about turning the A/C on it almost stalls the car instantly. Any ideas???

the blue 32 wrote: ↑

Fri Sep 13, 2019 3:46 pm

I have no idea what's going on with my 1990 nissan 300zx NA. I have another motor in it (motor has about 150,000 miles) and anything under 3k rpm it chugs like hell and almost stalls itself. And dont even think about turning the A/C on it almost stalls the car instantly. Any ideas???

Well it could be one of your cylinders is misfiring from a bad spark plug or ignition coil. Do you by any chance have a OBD reader? I had the same problem in my 94 Z32 NA and I changed the spark plugs and gapped them to the recommended spec and it idled and ran fantasic!

Most likely the MAF sensor, try a good known one. Make sure it’s an oem Nissan n62 with the orange label. Or a very large vacuum leak.

itsa300zx wrote: ↑

Fri Sep 13, 2019 7:46 pm

Most likely the MAF sensor, try a good known one. Make sure it’s an oem Nissan n62 with the orange label. Or a very large vacuum leak.

I agree with this, the connector can be corroded as mine was recently, and which caused it to not accelerate and nearly die when the accelerator was released. I quick clean and di-grease immediately solved the issue. The MAF could also be dirty, a shot or two of MAF cleaner from Autozone has worked for me in this case.
If nothing here works, look for corrosion of PTU, CAS, IACV/etc. connectors and clean as necessary. As mentioned vacuum hoses could be a vac leak, and ensuring viability of all other service items would be another next step.
Hope this helps!