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.
Trouble code P0300 means: Random/multiple cylinder misfire detected
Random misfire, cylinder 2 misfire, and cylinder 3 misfire. see related question below.
It means that more than one cylinder has a misfire history. PO301 would be cylinder number 1 misfire. PO302 would be number 3 cylinder misfire.
po300-Random/multiple cylinder misfire detected. po303-Cylinder no. 3 misfire detected. po306-cylinder no. 6 misfire detected po300-Random/multiple cylinder misfire detected. po303-Cylinder no. 3 misfire detected. po306-cylinder no. 6 misfire detected
answer : Random Misfire
Tune up
You locate the cause of the random misfire and take corrective actions against that; be it a coil, plug, wire, coil boot or crank sensor. A random misfire is as it states - a misfire that happens randomly in possibly a random cylinder as well. They can be hard to diagnose, as well and it is recommended that you take vehicle to a qualified, ASE certified shop for diagnostics.
P0300 is multiple or random cylinder misfire.
P0303 is cylinder #3 misfire. P0300 would be random misfire. Either way you need to diagnose the case of a misfire. Check spark plugs, plug wires(if equipped), cylinder compression, fuel inectors, and wiring.
Multiple or random cylinder misfire.
random/multiple cylinder misfire!
Random cylinder misfire