Service manual

G424F(FE) Service Manual 240 Chapter 8. Basic Troubleshooting
Backfire
Fuel ignites in intake manifold or in exhaust system, making loud popping noise.
PRELIMINARY CHECKS
Perform the visual checks as described at start of “ Basic Troubleshooting” chapter.
Simulate condition by reviewing operation procedure practiced by vehicle operator.
PROBABLE CAUSE CORRECTIVE ACTION
Fuel system
malfunction
Perform fuel system diagnosis check:
• Check for fuel leaks
• Check for MIL faults
• Check for damaged components
Ignition system
malfunction
Check proper ignition coil output voltage with spark tester.
Check spark plugs. Remove spark plugs, check for wet plugs, cracks, wear,
improper gap, burned electrodes, or heavy deposits. Repair or replace as
necessary.
Check spark plug wires for crossfire; also inspect distributor cap, spark plug
wires, and proper routing of plug wires.
Check ignition timing. Refer to application manual.
Engine mechanical
Check compression: look for sticking or leaking valves.
Check intake and exhaust manifold for casting flash and gasket
misalignment.
Refer to Chapter 3 Engine Mechanical System.
Related MIL Faults: EST faults / ETC faults / Encoder error
Pre-catalyst O2 sensor faults
Dieseling, Run-on
Engine continues to run after key is turned “OFF,“ but runs very roughly. If engine runs smoothly, check
ignition switch and adjustment.
PRELIMINARY CHECKS
Perform the visual checks as described at start of “ Basic Troubleshooting” chapter.
PROBABLE CAUSE CORRECTIVE ACTION
Fuel system
malfunction
Check for fuel leaks or leaking injector.
Ignition switching Make sure power to system is shut off when key is in OFF position.
Fuel lock off valve Make sure lock off valve is closing properly.
Ignition system malfunction Check spark advance at idle.
Related MIL Faults: EST faults / ETC faults / Pre-catalyst O2 sensor faults