Checks
| Action
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DEFINITION: The vehicle has a momentary lack of response
when depressing the accelerator pedal. The condition can occur at any
vehicle speed. The condition is usually most severe when attempting
to make the vehicle move, as from a stop sign. The condition may cause
the engine to stall if it is severe enough.
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Preliminary Checks
| Refer to Important Preliminary Checks in
Symptoms
.
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Fuel System Checks
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| | Check for low pressure during moderate or full throttle acceleration.
If the fuel pressure drops below specification, there is possibly a low or
high pressure regulator fault or a fuel system restriction. |
| • | Check for proper EVAP purge system operation. |
| • | Check for proper installation of the gas distribution adaptor
(GDA). |
| • | Check for air leaks at the GDA. |
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Sensor Checks
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| • | Check for proper TP sensor operation. A TP sensor that does not
respond quickly and accurately to throttle plate movement may cause this symptom. |
| • | Check for proper MAP sensor operation. A MAP sensor that does
not respond quickly and accurately to manifold pressure changes may cause
this symptom. |
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Ignition System Checks
|
| | Important:: A higher secondary ignition voltage is required to operate the vehicle
on CNG than on gasoline. A vehicle that operates normally on gasoline does
not indicate a fully functional ignition system.
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| • | Check for proper secondary ignition system voltage output using the
J 26792 spark tester. |
| • | Check for fouled spark plugs. |
| | If fouled spark plugs are indicated the reason for the fouling must
be found and corrected. |
| • | Check for faulty spark plug wires. |
| • | Check for an open ignition system ground (if equipped). |
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Additional Checks
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| • | Check Service Bulletins for control module (AF ECU, VCM/PCM or
ECM ) programming updates (re-flashing). |
| • | Check for manifold or air induction system leaks. |
| • | Check for proper generator operation. |
| • | Check for proper EGR valve operation. An EGR valve that opens
too quickly or opens more than desired may cause this symptom. |
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