Checks
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DEFINITION: The vehicle has a momentary lack of response when pushing down on the accelerator pedal. The condition can occur at any vehicle speed. The condition is usually most severe when trying to accelerate the vehicle from a stop. The condition may
cause the engine to stall.
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Preliminary Check
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Fuel System Checks
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| • | Check for a restricted fuel filter. Check for the correct fuel pressure. Refer to
Fuel System Diagnosis . |
| • | Remove the air cleaner cover and observe the fuel injector for a conical spray pattern with increased flow when accelerating the engine. |
| • | Check that the fuel injector electrical resistance is 0.5-1.5 ohms at 20°C (68°F). |
| • | Check for water contamination of the fuel. |
| • | Check the TP sensor for binding or sticking. Voltage should increase at a steady rate as throttle moves toward wide open throttle (WOT). |
| • | Check the MAP sensor for a quick and accurate response to changes in intake manifold pressure. |
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Ignition System Checks
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| • | Check for adequate secondary ignition voltage with a
J 26792 spark tester or an equivalent. |
| • | Check the spark plugs for any of the following conditions: |
| - | Wet (fuel fouled) plugs. |
| - | A terminal screw that is bent or loose (rotate and pull). |
| - | A ceramic insulator that has cracks, carbon tracking or deposits (red or black dust) |
| - | A tip insulator that has cracks, carbon tracking, deposits (oil, carbon, glazing, fuel additive), or is loose (rattles). |
| - | A center electrode that is loose (wiggles side to side) |
| - | An incorrect spark plug gap that is too large or too small. |
| - | Platinum pads that are missing. |
| • | Check for bare or shorted ignition wires. |
| • | Check for moisture in the distributor cap. |
| • | Check for faulty spark plug wires. |
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Additional Checks
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| • | Check for Service Bulletin updates. |
| • | Check the generator output voltage. |
| • | Check the EGR valve operation. After the other checks in this table have been performed, disconnect the EGR valve and road test the vehicle. A hesitation that was eliminated may have been caused by the EGR valve flowing too much or too soon. A partially
restricted exhaust system may cause enough exhaust backpressure to affect normal EGR valve operation. Refer to
Restricted Exhaust System Check in order to check for excessive exhaust system backpressure. Refer to
Exhaust Gas Recirculation (EGR) System Diagnosis in order
to check for normal EGR system operation. |
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