I have had a problem with my ranger for quite a while now well its so bad now it doesn't have enough power to start on a hill or cant go up one well here is the issue the motor sound like its misfiring shakes doesnt have any power at all i have replaced plugs,wires,coils,egr valve,catalytic converter,oxygen sensor,erg pressure sensor and battery and some times the voltage gauge will bounce and i have a PVC valve for it but cant find the valve it self i just have no idea what else it could be Thanks