I recently replaced the head gasket and VSS on my 95 Legend. Now I'm getting a check engine light with codes 23 & 53 (right and left knock sensors). The check engine light comes on after driving a mile or two (not immediately). It seems to start and run fine, though the throttle surges/pumps when it is restarted warm and left in park.

Can you help me diagnose whether this is caused by: (1) damaged knock sensors, (2) a problem with knock sensor wiring, (3) actual engine knocking or other problem the sensors are designed to detect, (4) air in the cooling system, or (5) something else? I would think that if the sensors were damaged or the wiring were wrong, the check engine light would come on immeadiately rather than waiting for the engine to warm up, but maybe that's incorrect.

If you can give me some pointers on how to proceed with diagnosing and fixing this, I will really appreciate it. Thanks

Doug