Nissan Repair: hesitation, crank angle sensor, mass air flow sensor

Question
i have a 1993 nissan d21 truck with a 4 cyl. truck starts and runs good for the first 8-10 miles then starts to hesitate and stumble on acceleration. i have replaced fuel filter and air filter. i have tested the coil, plugs, wires, dis cap, and crank angle sensor. the primary voltage on the coil was good but the ohm reading was barely out of tolerance. it was 1.1 ohms when the upper limit is 1 ohm. the secondary voltage was also good and ohm reading was in the middle of the scale. i also checked the cat converter. i drilled some holes in it and it ran good for a few days. i am going to replace it this week but do you know of something else i need to check? it acts like its getting enough fuel but maybe not enough air flow?

Answer
Hi there, seems like the motor is acting up when it warms up and goes into closed loop operation. The prime suspects are the TPS and the MAF sensors. (Throttle Position Switch and Mass Air Flow Sensor). Drilling holes in the CAT is never a good Idea because it destroys it further in case that it was already damaged. Please replace the CAT and check exhaust system for restrictions/blockages. The TPS and MAF sensors need to be checked also. These tests can be performed by a qualified auto technician.