Aiites..here the deal. My car would lag in acceleration from 2k-3200rpm. It like whenever I accelerate in any gear something is like holding the car back, but after I get pass the 3,200 rpm the car will regain its acceleration back. I know it not the cap, rotors, spark plug wires, or spark plugs. Well I try to reset my ecu and the car will drive fine for a while, but whenever the hesitation cames back, a cel light would pop up. It turn out to be a code 63-secondary o2 sensor. I searched everywhere and everybody mention that a code 63 shouuldn't mess with the car performance? Are they wrong or it is indeed my secondary o2 that need replacing? I'm running a 4-1 jdm header, jdm cat with a second o2 bung after the cat.

 

What car, what motor, and what OBD?? The 02 sensor will definitely cause hesitation. It's happened to me a few times. I've destroyed three so far. Two from running leaded fuel, and one from spraying N20.

 

1998 gsr motor with a 4-1 jdm header, jdm cat, and I welded the second o2 bung after the cat on the b pipe itself...So it probaly is indeed my o2 that is bad huh? It is just so confusing, because some people mention that a secondary o2 cel light does not hurt the performance.