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Home >> Saturn >> 2000 >> SW2 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0300: Engine Misfire Detected >> Diagnostic Procedures
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Diagnostic Procedures

  1. Connect scan tool. Start engine and operate for one minute. Check if any active misfire DTCs are present. If DTCs are present, go to next step. If DTCs are not present, problem is intermittent. See DIAGNOSTIC AIDS  .
  2. Using scan tool, monitor MISFIRE CURRENT CYLS #1-4. If misfire counters for cylinders 1-4 is randomly filling up or paired cylinders No. 1-4 and No. 2-3 misfire counters is filling up, go to step  4 . If cylinders No. 1-4 or paired cylinders No. 1-4 and No. 2-3 misfire counters is not filling up, go to next step.
  3. Check if specific cylinder misfire counter is filling up. If misfire counter is not filling up, problem is intermittent. See DIAGNOSTIC AIDS  . If misfire counter is filling up, go to step  7 .
  4. Check for vacuum leaks, faulty spark plug wires or fuel quality. Repair as necessary. Recheck misfire counter. If random misfire is present, go to next step. If paired misfire is present, go to step  6 .
  5. Check fuel pressure. Fuel pressure should be 38-44 psi (13-14 kg/cm2 ). Check for open EGR valve or gasket. Check for fouled or incorrectly gapped spark plugs. Check coil resistance (6500-11,500 ohms tower-to-tower). Check for clogged fuel injector. Perform fuel injector balance test. See appropriate SYSTEM & COMPONENT TESTING article. Check sticking valve. Repair as necessary.
  6. Perform crankshaft learn procedure. Check for intermittent open or short to ground or short to voltage in IC circuits No. 1-4 and No. 2-3. Check coil secondary resistance (6500-11,500 ohms tower-to-tower). Check for carbon tracking or corrosion on coil towers. Repair or replace as necessary.
  7. Check for aching spark plug wire. Wire resistance should be 1500-15,000 ohms. Check for carbon tracking or corrosion on spark wire ends. Check for fouled or incorrectly gapped spark plugs. Check for clogged fuel injector. Perform fuel injector balance test. See appropriate SYSTEM & COMPONENT TESTING article. Check sticking valve. Check fuel injector resistance. Resistance should be 11.8-12.6 ohms. Check engine compression. Normal compression should be 185-205 psi (13-14 kg/cm2 ). Repair as necessary.
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