Spectrum 3.0L GM - Lack of Power, Sluggishness, or Sponginess

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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 throttling the engine.

Preliminary Checks

 Refer to the Fuel system OBD System Check.

 Compare the customer’s engine with a similar unit to verify customer has

an actual problem. Do not compare the power output of the engine op-

erating on Natural Gas and Propane to one operating on gasoline as the

fuels do have different performance 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 pres-

sure. Refer to LPG Fuel System Diagnosis.

 Check for the proper ignition output voltage with the spark tester J 26792

or the equivalent.

 Check the Regulator and Throttle body for proper installation and lea-

kage. Check all air inlet ducts for condition and proper installation.

 Check all air inlet ducts for condition and proper installation.

 Check for fuel leaks in supply lines.

 Verify that the Fuel Supply Valve on the supply line is open.

 Verify that liquid fuel (not vapor) is being delivered to the Regulator.

Sensor Checks

 Check the Heated Exhaust Gas Oxygen Sensor (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.