Checks
| Action
|
Definition: Engine
power variation under steady throttle or cruise. Feels like the vehicle speeds
up and slows down with no change in the accelerator pedal.
|
Preliminary
|
| • | Refer to Important Preliminary Checks
. |
| • | Refer to Visual/Physical Checks
. |
| • | Be sure driver understands transmission torque converter clutch,
and A/C compressor operation as explained in the owners manual. Inform customer
how TCC and the A/C clutch operates. |
|
Sensor/System
|
| • | 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
HO2S may exhibit abnormal discoloration on the portion of the sensor that
is exposed to the exhaust stream. Silicon contamination causes a high but
false HO2S signal voltage (rich exhaust indication). The PCM will reduce
the amount of fuel delivered to the engine, causing a severe driveability
problem. Refer to Heated Oxygen Sensor(s) in
Information Sensors
. |
| • | Check MAF Sensor and related wiring. |
| • | Check the EGR valve for a stuck open pintle. |
|
Fuel System
|
| • | Check the fuel pressure. |
| • | Ensure each injector harness is connected to the correct injector/cylinder.
Refer to
Engine Controls Schematics
Wiring
Diagrams. |
| • | 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 Fuel Trim System Rich
. |
| • | 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 Fuel Trim System Lean
. |
|
Ignition System
|
| • | Check for proper ignition voltage output using the following steps: |
| - | Clip the spark tester J 26792 to engine ground. |
| - | Connect one end of a spark plug wire to the 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 spark tester; a crisp blue
spark should be observed. |
| - | Repeat the above steps for each coil. |
| • | If adequate 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 - 8000 ohms (5K - 8K ohms). | - | Spark Plug wires - Signs of arcing/cross firing, cracks, carbon
tracking, plug boot damage, pinched, improper routing, or high resistance. |
| - | Spark plug wire resistance should measure less than than the specified
value. |
VIN 1 Spark Plug Wire Resistance
7000 ohms (7K ohms).
VIN K Spark Plug Wire Resistance
10000 ohms (10K ohms).
| | 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 malfunctioning.
|
| - | Ignition System Wiring - Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and check for the following conditions: |
| - | 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. |
|
Additional Checks
|
| • | Check TCC operation. Refer to 4T65-E
Automatic Transaxle Diagnosis
. |
| • | Check the exhaust system for a possible restriction: |
| - | Inspect exhaust system for damaged ro collapsed pipes. |
| - | Inspect muffler for heat distress or possible internal failure. |
|
