93 Nissan Pathfinder 4x4 xe automatic trans. Missing below 2k rpm. Replaced cap, rotor, and wires. cleaned egr. cleaned throttle body. checked vacuum lines.Smooths out above 2k rpm.

check coil and distributor for output

have you checked the coil?

Have u checked the cadeletic converter. It can do funny things

spark plugs weak pump

run the fault codes to find which sensor is failing from internal heat build up
when allowed to cool it works fine until it gets hot again

Clean the throttle body. Check the mass air flow sensor for corrosion of the wire harness connector.

Good Evening, have you double checked your timing and checked for possible vacuum leaks?

The major causes of backfires are:

1) Emission control system not fuctioning properly.
2) Ignition timing is incorrect.
3) Faulty secondary ignition system; cracked spark plug insulator, faulty plug wires, distributor cap and/or rotor.
4)Fuel injection system malfunction.
5) Vacuum leak at fuel injectors, intake manifold or vacuum hose.
6) EGR stuck open all the time.

Check the vacuum line to the fuel pressure regulator and check to see if the fuel pressure regulator has gone bad. Give the throttle body a good cleaning and the injectors too. Do not use carb cleaner, it's to corrosive for the gaskets used in the throttle body. The other thing too that would cause this is a stuck or bad EGR valve, Try cleaning the EGR valve too since your cleaning the throttle body. Good luck and keep me posted.

Spray the intake with carb cleaner to find the vacuum leak. Check where the EGR mounts and the throttle body gasket sense you had both off.