TP-6903 5/16a Fuel System Troubleshooting 57
3.11. Hunting and Surging
Definition: The engine has a power variation under a
steady throttle. The engine feels as if it speeds up and
slows down with no change to the throttle.
Figure 3-13 Hunting and Surging Troubleshooting
Checks Action
Preliminary Checks None.
Sensor Checks Check the Heated Exhaust Gas Oxygen Sensor (HEGO) performance.
Fuel System Checks
Check for rich or lean symptom that causes the condition.
While running the engine, monitor the HEGO sensor.
Check the fuel pressure while the condition exists.
Verify proper fuel control shut-off valve operation.
Verify that the fuel supply valve on the gas supply line is fully open.
Ignition System Checks
Check for proper ignition output voltage with a spark tester.
Verify that the spark plugs are the correct type and properly gapped.
Remove the plugs and inspect them for the following conditions:
o Wet plugs (oil fouling).
o Cracks.
o Wear.
o Improper gap.
o Burned electrodes.
o Heavy deposits.
Check the Crankshaft Position (CKP) sensor.
Additional Check
Check that the ECM grounds are clean, tight, and in their proper locations.
Check the alternator output voltage.
Check the vacuum hoses for kinks or leaks.
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