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
  1. Start with: pull all spark plugs, inspect tip — replace full set to OEM spec gap
  2. Swap ignition coil(s) sequentially to identify a faulty coil; replace confirmed bad coils
  3. Compression-test all cylinders; readings below 150 psi (or >10% variance) indicate internal engine wear
  4. Check fuel pressure AND volume (flow test); replace pump if pressure drops under load
  5. If oil-related: change oil + filter, run with proper viscosity, recheck for lifter tick
Vehicles Affected
chevy ford dodge jeep gmc toyota honda bmw
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