Need help 300zx limits it's RPMs

[Laloz32]

I have 1990 300zx none turbo. The car runs fine when you start it you can rev it up to 4000 rpms with no problems. Once it runs for a bit and is at normal operating temp if you rev it up once you get to 3000 rpms it starts to bog down and you can hear a popping in the exhaust system. If you are driving the car you have no power once you it 2500 - 3000 rpms you can put the pedal to the floor and nothing happins. I was wondering if it would be the fuel pump or the pressure regulator. If the fuel pump why would it run fine at the start then act up if it was bad would it not be bad all the time.

[itsa300zx]

Most likely MAF related.

[elecfus]

you've hit the limp home mode. read the engine codes.
if you dont have a consult cable, make a jumper using insulated spade terminals and a wire. insulated terminals are important because you can short the consult if you bump the connector and short pins.

[DCaff300ZX]

Both good answers, try the cheap and easy first and get some MAF cleaner from Autozone and carefully remove the MAF and clean it as per instructions- don't get crazy with it, just a few sprays facing down so any excess runs out before it quickly dries. It can't hurt to change the filters either if they are dirty. If you have a dirty MAF issue you should have fixed it- also be sure to check the connector for green corrosion while doing the job.

If above no help, do as elecfus says and read your engine codes, a very easy job actually.
There is a board under the passenger footwell carpet you remove to access the ECU, and a small screw with an arrow on the side that you turn and hold as directed, then return to former position. The dash CEL will blink a number of times, which is a code: 3 blinks then a pause followed by 3 blinks and a long pause, then repeated, is a code 33, bad ps O2 IIRC. 5 blinks and then 5 again is a 55, no problems. Be careful to count carefully, as two different number sequences or more is two or more codes which is quite possible, where first blinks still are the first code number and second blinks the second code number. Be sure to watch the sequence(s) many times to ensure that you have the correct code(s) before returning the potentiometer (screw) back to normal position.
Check the fsm or osm for these codes and what they refer to, and use the osm/fsm tests to check them to find/isolate your issue, and save a TON of wasted money ($100 just for the codes at Nissan! And then they can't tell you what they mean...) you would have now spent at any other shop! OSM is available to download in our "everything you need....Z32" sticky.
Armed with the info you will get from this, we will be able to better answer your coming questions as you narrow this b**tch down.

[Bobbymudd]

Hey sorry to hear about you problem. I had a very similar problem with my Z. It would start up and run fine. Then I couldn't rev to 4000, then it would warm up more and it would be 3000, and so on. How ever my car wouldn't pop and sputter, it would feel like a really soft rev limiter. It ended up that my fuel pump was on the way out. Replaced it and haven't had a problem since. Hope this helps and hope you figure out your problem man, good luck.

[SleepyN/A]

Take a look at your tps plug, I have a pretty similar problem and I believe I found out why. My connector had one of the prongs corroded completely out