Checks
| Action
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DEFINITION: The vehicle has a momentary lack of response when depressing
the accelerator. The condition can occur at any vehicle speed. The condition
is usually most severe when trying to make the vehicle move, as from
a stop. The condition may cause the engine to stall if it's severe enough.
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Preliminary Checks
| Refer to
Symptoms
.
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Fuel
System Checks
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| • | Inspect for low fuel pressure during a moderate or full throttle
acceleration. Inspect for a possible faulty low or high pressure regulator
or a restriction in the fuel system if the fuel pressure drops below
specification. |
| • | Inspect the Throttle Position (TP) sensor for binding or sticking.
Voltage should increase at a steady rate as the throttle moves toward Wide
Open Throttle (WOT). |
| • | Verify the Manifold Absolute Pressure (MAP) sensor response and
accuracy. Refer to DTC P0106 MAP Systems Performance in Engine Controls -
5.0, 5.7L in the C/K Truck Service Manual. |
| • | Inspect the canister purge system for proper operation. Refer
to EVAP Control System Diagnosis in Engine Controls - 5.0, 5.7L in the
C/K Truck Service Manual. |
| • | Inspect the Gas Distribution Adapter (GDA) for proper installation
and leakage. |
| • | Verify the correct bi-fuel VCM software is installed. |
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Ignition System Checks
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Important:: CNG is a gaseous fuel and requires higher secondary ignition system
voltages for the equivalent gasoline operating conditions. Do not discount
the possibility of a CNG-only ignition system failure if a problem is
reported on the CNG system and not on the gasoline system. Test the
system accordingly.
| • | Inspect for the proper ignition voltage output with the J 26792
Spark Tester or the equivalent. |
| • | Inspect the CMP adjustment. |
| • | Verify for faulty spark plug wires. |
| • | Inspect for fouled spark plugs. |
| • | Inspect for an open ignition system ground. |
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Additional Checks
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| • | Inspect the service bulletins for PROM updates. |
| • | Inspect for manifold vacuum or air induction system leaks. |
| • | Verify the generator output voltage. |
| • | Inspect the EGR valve operation. Refer to EGR System Diagnosis
in Engine Controls - 5.0, 5.7L in the C/K Truck Service Manual. |
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