Impco HHI, Service Manual

Page: 49 / 485

49
LACK OF POWER, SLUGGISHNESS, OR SPONGINESS
Checks Action
DEFINITION: The engine delivers less than expected power. There is little or no increase in speed
when partially applying the accelerator pedal.
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 oper-
ating 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 pre s-
sure. 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 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 contamina-
tion 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 fail-
ure.

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 loca-
tions.

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 sus-
pected circuit and/or systems.

Check the DST data.