2002 Nissan Xterra Q&A

2002 Nissan Xterra Question: need help with code#4 misfire&throttle positioner switch codes and poor running

I have replaced spark plugs,wires,cap,rotor,fuel&air filters.My friend purchased vehicle last week.It had #4 misfire code & knock sensor code.I replaced knock sensor and gaskets found no cracked vac lines but she still runs poorly @idle.I added Lucas fuel treatment and dry gas with 10 gallons 93 octane.I did a cylinder compression test on 4 it was 125 lbs.Is there any problems with wiring harness or injector problems? -
Answer 1
Engine size?? Also 125 psi aint a bunch but should fire the cylinder. Other comp. readings? Smooth out with slight throttle? -
Comment 1
3.3 i replaced the throttle postion switch also i didnt check comp on the other cyl it does smooth out with throttle do i need to change injector? -
Comment 2
Compression readings for other cylinders would be very helpful. Or at least 2 & 6. The other two, front and back, of the one you checked. -
Answer 2
code be $4 ign or inj circuit is bad. rec your seek help from your mech as to not waste time and money -
Comment 1
i pulled plenum again changed injector runs great no codes thanks -