Diagnostic Aids
WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.
Scan tool message MISFIRE CUR. #1-6 is helpful for determining if only a single cylinder is affected by misfire. If scan tool displays MISFIRE CUR. #1-6, check suspect ignition coil for cracks or damage. If problem is present, substitute a known-good ignition coil, or swap ignition coils cylinder-to-cylinder. If misfire follows coil, replace suspect ignition coil.
If misfire is random check following:
- Check PCM and system grounds. Ensure that all grounds are clean and secure.
- Check MAF sensor. See SYSTEM & COMPONENT TESTING article.
- Check for disconnected or damaged vacuum hoses. Check for vacuum leaks at EGR valve, throttle body and intake manifold.
- Perform FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in BASIC DIAGNOSTIC PROCEDURES article. Check for faulty fuel pump, plugged fuel filter or suspect fuel pressure regulator.
- Check fuel injectors. Perform FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. Also check condition of fuel injector "O" ring seals.
- Check EGR valve. Check for leaking valve, adapter and feed pipes. See SYSTEM & COMPONENT TESTING article.
- Check fuel quality. Fuel with wrong octane rating may cause driveability issues.
- During transportation of vehicle from assembly plant to dealership can involve as many as 60 ignition cycles while only driving 2-3 miles. This can result in fouled spark plugs, causing MIL to illuminates and DTC P0300 to set.