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
|
| | Important:: Do not compare the power output of the vehicle while operating on CNG
to a vehicle operating on gasoline. Both fuels have different drive
feel characteristics.
|
| • | Verify the customers concern by comparing the power output of a similarly
equipped known good vehicle to the suspect vehicle. |
| • | Inspect the air filter for proper type and for dirt or restriction. |
| • | Test the transmission for proper shift pattern and downshift operation. |
| • | Inspect the PCM for the correct CNG calibration. Program the PCM
if necessary. |
|
Fuel System Checks
|
|
Ignition System Checks
|
| | Important:: A higher secondary ignition voltage is required to operate the vehicle
on CNG than on gasoline.
|
| • | Test for proper secondary ignition system voltage output using only
the J 26792
Spark Tester. |
| | Important:: More timing advance is required to operate the vehicle on CNG than on
gasoline.
|
| • | Test for proper operation of the Knock Sensor system. |
|
Exhaust System Checks
| Inspect the exhaust system for a possible restriction.
Restrictions can include the following:
| • | A failed catalytic converter |
| • | Damaged or collapsed pipes |
| • | An internally failed muffler -- may show signs of heat distress |
|
Engine Mechanical Checks
| Test for proper engine operation by checking for the following:
| • | Correct engine compression |
| • | Correct engine valve timing |
| • | A worn or incorrect camshaft |
|
Additional Checks
|
| • | Test for proper A/C compressor clutch operation. An A/C clutch
that is engaged all the time may cause this symptom. |
| • | Test for proper transmission torque converter clutch (TCC) operation,
if equipped. |
| • | Test for proper generator operation. |
| • | Inspect for proper operation of the accelerator pedal. A stretched
accelerator cable may cause this symptom. |
|
