Car not running anywhere close to right.

[freeandam]

I have a '90 S13 with the SOHC Ka. The car is definitely not running right. the idle goes back and forth from around 500 to 1000 on the nose. When I give it gas in the lower rpm range sometimes it wants to go and sometimes it bogs down bad. In the higher rpm range it feel like my fuel cuts off randomly for a few seconds at a time. It's completely random. Even with the pedal to the floor it does nothing for a few seconds. It also has trouble revving anything past around 4k. The more I give it throttle the more it wants to fall on its face. The only way to get it to rev is slowly apply throttle. If I do it all at once it won't rev. I've replaced the Plugs, Plug Wires, Distributor cap and rotor, fuel filter, M.A.F sensor, and manually pulled the injectors and cleaned them. I pulled the fuel pump today and the fuel sock was clean. I'm not sure if the pump is going out or not. I also ordered an O2 sensor that will be replaced tomorrow but I have a feeling it's more than that. I am just out of ideas on what this could be. Thanks in advance for any help.

[PapaSmurf2k3]

Is the ECU throwing any codes?

[freeandam]

I checked it and its not throwing any codes.

[freeandam]

Go it. It was the O2 sensor. Turns out it was the original from Nissan

[PapaSmurf2k3]

Sweet! Congrats!

[freeandam]

Ugh It worked right at first but now its exhibiting some of the same symptoms. Not sure what to do. It's better but still not right....I no longer have trouble in the lower rpms and I go through first gear like it should, all the way to the rev limiter but from 2nd onwards it seems like my throttle is cut from around 4k on and if it isn't cut the car is struggling to move.

[PapaSmurf2k3]

You might want to reset the ECU so it will unlearn all the bad stuff from the old O2 sensor.

Just unplug the battery for ~20 minutes.

[freeandam]

Will try it. I remember reading it after disconnecting the battery over a month ago and the only code it threw was the one for "no faults." I'm not sure anything will be different this time but trying it doesn't hurt anything.

[PapaSmurf2k3]

Yeah, that clears whatever codes are in there, but it also usually sets the maps back to factory default.

[freeandam]

OK cool. I'll disconnect it tomorrow. could it possibly be something like the timing being off or anything. everything sounds right but I don't know much about it.

[PapaSmurf2k3]

Yeah. It could absolutely be valve timing or ignition timing.

[freeandam]

How do I go about checking those or knowing if it's off in the first place?

[PapaSmurf2k3]

You'll need a timing light for the ignition timing. I'm not sure about the cam position at TDC for the single over head cam engines, but I'm sure you can find that info in the factory service manual. There should be a link to them in my signature.