Fast root-cause diagnosis
BlueDriver Bluetooth Pro
Guided reports and easier interpretation for most DIY users.
Check Price P0300
Random / Multiple Cylinder Misfire
🔴 CRITICAL — STOP DRIVING POWERTRAIN · Ignition System
PCM detected misfires on multiple cylinders—no single cylinder is consistently misfiring.
What You'll Notice
- Severe rough idle — cabin vibration noticeable
- Flashing MIL (catalytic converter protection mode)
- Power loss across RPM range
- Rotten-egg smell from exhaust (unburned fuel hitting cat)
- Possible stall at idle
Probable Causes
- Distributor cap or high-tension leads cracked/arcing
- Worn or incorrectly gapped spark plugs across all cylinders
- Low compression across multiple cylinders — worn rings or burnt valves
- Injector rail pressure drop — failing fuel pump or pressure regulator
- Bad ignition coil pack or failing crankshaft position sensor
- Contaminated engine oil causing hydraulic lifter collapse (GM V8)
Direct Repair Steps
- Start with: pull all spark plugs, inspect tip — replace full set to OEM spec gap
- Swap ignition coil(s) sequentially to identify a faulty coil; replace confirmed bad coils
- Compression-test all cylinders; readings below 150 psi (or >10% variance) indicate internal engine wear
- Check fuel pressure AND volume (flow test); replace pump if pressure drops under load
- If oil-related: change oil + filter, run with proper viscosity, recheck for lifter tick
RECOMMENDED SCANNER
BlueDriver Bluetooth Pro OBDII Scanner
Reads P0300 and 5,000+ codes. Live data, enhanced
diagnostics, repair reports. Works on all 1996+ vehicles.
View on Amazon →
Best Scanner Pick for P0300 Workflows
Advanced troubleshooting
OBDLink MX+
Higher data refresh speed for deeper live-data analysis.
Check Price