Operation Section
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LACK OF POWER, SLUGGISHNESS, OR SPONGINESS
Checks Action
DEFINITION: The engine delivers less than expected power.
Preliminary Checks
• Refer to the LPG Fuel system OBD System Check.
• Compare the customer’s vehicle with a similar unit to verify customer has an
actual problem. Do not compare the power output of the vehicle operating on
LPG to a vehicle operating on gasoline as the fuels do have different drive feel
characteristics.
• Remove the air filter and check for dirt or restriction.
• Check the vehicle transmission.
• Refer to the OEM transmission diagnostics.
Fuel System
Checks
• Check for a restricted fuel filter, contaminated fuel, or improper fuel pressure.
Refer to LPG Fuel System Diagnosis.
• Check for the proper ignition output voltage with the spark tester J 26792 or the
equivalent.
• Check for proper installation of the mixer assembly. Check all air inlet ducts for
condition and proper installation.
• Check for fuel leaks between the EPR and the mixer.
• Verify that the LPG tank manual shut-off valve is fully open.
• Verify that liquid fuel (not vapor) is being delivered to the EPR.
Sensor Checks
• Check the Heated Exhaust Gas Oxygen Sensors (HEGO) for contamination and
performance. Check for proper operation of the TMAP sensor.
• Check for proper operation of the TPS and FPP sensors.
Exhaust System
Checks
Check the exhaust system for a possible restriction:
• Inspect the exhaust system for damaged or collapsed pipes.
• Inspect the muffler for signs of heat distress or for possible internal failure.
• Check for possible plugged catalytic converter.
Engine Mechanical
Check
Check the engine for the following:
• Engine compression.
• Valve timing.
• Improper or worn camshaft.
• Refer to Engine Mechanical in the Service Manual.
Additional Check
• Check the ECM grounds for being clean, tight, and in their proper locations.
• Check the alternator output voltage.
If all procedures have been completed and no malfunction has been found, review
and inspect the following items:
• Visually and physically, inspect all electrical connections within the suspected
circuit and/or systems.
• Check the DST data.
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