| |
|
Hesitation, Sag, Stumble
News
Low Mount 3800 ALT!
Low mounts in stock today. Newest design has
tension belt assembly, cleaned, and blasted.
|
Checks |
Action |
|
DEFINITION: Momentary lack of response when the accelerator is pushed
down. This condition can occur during any vehicle speed. The condition
is usually more pronounced when the driver first attempts to make the
vehicle move, such as during acceleration from a stop sign. This
condition can cause the engine to stall if the condition is severe
enough. |
| Preliminary |
|
• |
Refer to Powertrain On Board
Diagnostic (OBD) System Check . |
|
• |
Refer to Important
Preliminary Checks. |
|
• |
Refer to Visual/Physical
Checks |
|
| Sensor/System |
|
• |
Test the Heated Oxygen
Sensor(s). The Heated Oxygen Sensors should quickly respond to
different throttle positions. If not, inspect the HO2S for
silicon or for other contaminants from the fuel or fro the use
of an improper RTV sealant. The sensors may have a white powdery
coating. Silicon contamination causes a high but false HO2S
signal voltage, indicating a rich exhaust. The PCM will reduce
the amount of fuel that is delivered to the engine, causing a
severe driveability problem. Refer to
Information Sensors/Switches Description - Heated Oxygen
Sensors. |
|
• |
Test the TP Sensor and test
the related wiring. |
|
• |
Test the MAF Sensor and test
the related wiring. |
|
• |
Test the EGR system for
proper operation. Refer to Exhaust Gas Recirculation (EGR)
System Description . |
|
| Fuel System |
|
• |
Test the fuel system for
contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel
Diagnosis Alcohol-in-Fuel Diagnosis . |
|
• |
Test the fuel injectors
using the following tests: |
|
- |
Fuel Injector Coil Test -
Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95
Degrees F) |
|
- |
Fuel Injector Coil Test -
Engine Coolant Temperature (ECT) Outside 10-35 Degrees C (50-95
Degrees F) |
|
- |
Fuel Injector Balance Test
|
|
• |
Inspect for conditions which
can cause an engine to run rich, indicating that the long-term
fuel trim is significantly in the negative range. Refer to DTC
P0172 Fuel Trim System Rich . |
|
• |
Inspect for conditions that
can cause an engine to run lean. indicating that the long-term
fuel trim is significantly in the positive range. Refer to DTC
P0171 Fuel Trim System Lean . |
|
| Ignition System |
|
• |
Test 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, and leave the other end of the spark plug
wire to the coil that is being tested.
- Connect one end of another
spark plug wire to the other coil tower, and connect the other end
of the spark plug wire to ground.
- Crank the engine while you
observe the spark tester. You should observe a spark.
- Repeat the above steps for each
coil.
|
• |
If no spark is present at
the coils, check for the following conditions: |
|
- |
The coils--Check for cracks,
for carbon tracking and arcing, or for a secondary resistance
value that is outside the specified range.
Coil Resistance
5000-8000 ohms (5K- 8K ohms) |
|
- |
The spark plug
wires--Inspect for signs of arcing or cross-firing, for cracks,
for carbon tracking, for plug boot damage, for pinches, for
improper routing, or for a resistance value that is outside the
specified range.
Spark Plug Wire Resistance
600 ohms per ft.
Important: Spraying
the secondary ignition wires with a light mist of water may help
to locate an intermittent problem. The ignition components will
arc to ground when a secondary component is faulty. |
|
- |
The ignition system
wiring--Inspect for a loose ignition module feed or ground
connection, or for damaged system wiring. |
|
• |
Remove the spark plugs and
inspect for the following conditions: |
|
- |
Burned or damaged electrodes
|
|
- |
Improper heat range or reach
|
|
• |
If the spark plugs are gas
or oil fouled, determine the cause of the fouling before you
replace the spark plugs. |
|
| |
