P0300 Diagnostic Code - Random Misfire
Symptoms.
Engine may stumble or miss
Engine may be hard to start
you may notice no issues
Cause
Failing spark plugs or spark plug wires
Bad coil or coil pack
Failing oxygen sensor(s)
Bad fuel injector or more than one
Stuck exhaust valve
Bad catalytic converter
EGR valve or valve passage clogging
Bad camshaft position sensor
Bad PCM or ECM
The Fix
Best first action is a tune up, new plugs, wires, inspect all hoses and wire connections then reset the code. If it returns you will need to narrow it down to a system, coils and coil packs should be tested, catalytic converters for function ( do you smell rotten eggs?). A misfire that jumps cylinders could indicate a lean condition, do you have any other codes along with the 300? this will help clue you in to the source, check valve function to make sure they are opening and closing fully.
This is probably pone of the most difficult codes to troubleshoot, so start with the basics and work your way into the more expensive options, in many cases a good old tune up solves the problem, back it up with a fuel system cleaning and see where you stand.
P0300 = Random/multiple misfire detected
P0300 means random misfire detected which probably has to do with the spark plugs or the plug wires
Code P0300 indicates a random misfire. - Haynes Repair Manual #36071, 1995-2005 Ford Ranger Pick-ups.
Random Misfire.
P0340 is error code for Camshaft Postion Sensor Circuit Malfunction
I noticed that question has already been correctly answered by Jrc405 on page 5 of the Ford Ranger XL Q & A
Trouble code P0701 means: Transmission control system,range or performance problem
Upstream Oxygen Sensor Circuit Slow Response (Bank 1)
Differential Pressure Feedback Electronic Sensor circuit Upstream Hose
P0500 is loss of vehicle speed signal. You need to test the speed sensor.
Trouble code P0442 means:Evaporative emission control system leak detected (Small leak)
P0300 - Random Misfire . P0300 indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring .