Checks
| Action
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DEFINITION: Momentary
lack of response as the accelerator is pushed down. Can occur at any vehicle
speed. Usually more pronounced when first trying to make the vehicle
move, as from a stop sign. May cause the engine to stall if severe
enough.
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Preliminary
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Sensor/System
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| • | Check the Heated Oxygen Sensor(s). The Heated Oxygen Sensors should
respond quickly to different throttle positions. If not, check the HO2S for
silicon or other contaminants from fuel or use of improper RTV sealant.
The sensors may have a white powdery coating. Silicon contamination
causes a high but false HO2S signal voltage (rich exhaust indication).
Refer to
Notice: Contamination of the oxygen sensor can result from the use of an inappropriate
RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption.
Remove the HO2S and visually inspect the portion of the sensor exposed to
the exhaust stream in order to check for contamination. If contaminated, the
portion of the sensor exposed to the exhaust stream will have a white powdery
coating. Silicon contamination causes a high but false HO2S signal voltage
(rich exhaust indication). The control module will then reduce the amount
of fuel delivered to the engine, causing a severe driveability problem. Eliminate
the source of contamination before replacing the oxygen sensor.
. The PCM will reduce the amount
of fuel delivered to the engine, causing a severe driveability problem.
Refer to Information Sensors - Heated Oxygen Sensor(s). |
| • | Check for 24X Crankshaft position and Camshaft position sensors
on scan tool. If both are not responding, check the sensor feed circuit (Both
sensors use a common feed circuit). |
| • | Check the TP Sensor and related wiring. |
| • | Check the MAF Sensor and related wiring. |
| • | Check the EGR system for proper operation. Refer to EGR System Description
. |
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Fuel System
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| • | Check items which can cause an engine to run rich (long term
fuel trim is significantly in the negative range). Refer to Diagnostic Aids
for DTC P0172. |
| • | Check items that can cause an engine to run lean (long term fuel
trim is significantly in the positive range). Refer to Diagnostic Aids for
DTC P0171. |
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Ignition System
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| • | Check for proper ignition voltage output using the following steps: |
| - | Clip the J 26792
Spark
Tester to engine ground. |
| - | Connect one end of a spark plug wire to the J 26792
Spark Tester, leave the other end of
the spark plug wire to the coil being tested. |
| - | Connect one end of another spark plug wire to the other coil
tower; connect the other end of the spark plug wire to ground. |
| - | Crank the engine while observing the J 26792
Spark Tester a spark should be observed. |
| - | Repeat the above steps for each coil. |
| • | If spark is not present at the coil(s), check for the following
conditions: |
| - | Coil(s)--Cracks, carbon tracking/arcing, or a resistance
value outside the specified range. |
Coil Resistance
5000-8000ohms (5K-8Kohms). | - | Spark Plug wires--Signs of arcing/cross firing, cracks, carbon
tracking, plug boot damage, pinched, improper routing, or a resistance value
outside the specified range. |
Spark Plug Wire Resistance
600ohms per foot (1 968ohms per meter).
| | Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition components will arc to ground
when a secondary component is faulty.
|
| - | Ignition System Wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and check for the following: |
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
| • | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
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