Hesitation, Sag, Stumble Symptom
Step
| Action
| Value(s)
| Yes
| No
|
DEFINITION: A momentary lack of
response as the accelerator is pushed down. This condition can occur at any
vehicle speed. his condition is usually most pronounced when you first
try to make the vehicle move, as from a stop sign. This may cause the engine
to stall if the condition is severe enough.
|
1
| Did you perform the On-Board Diagnostic (OBD) System Check?
| --
|
Go to Step 2
| Go to
Powertrain On Board Diagnostic (OBD) System Check
|
2
|
- Perform a bulletin search.
- If a bulletin that addresses the symptom is present, correct the
condition as instructed in the bulletin.
Did you find a bulletin that addresses the symptom?
| --
|
Go to Step 16
|
Go to Step 3
|
3
| Did you perform a
visual/physical check?
| --
|
Go to Step 4
| Go to
Symptoms
|
4
|
- Check the heated oxygen sensors (HO2S). The heated oxygen sensors
(HO2S) should respond quickly to the different throttle positions. If the
sensors do not respond to the different throttle positions, check the HO2S
for silicon or other contaminants from the fuel or the use of the improper
RTV sealant. The sensors may have a white powdery coating. Silicon contamination
causes a high but false HO2S signal voltage (rich exhaust indication).
The ECM will then reduce the amount of the fuel that is delivered to the
engine, causing a severe driveability problem.
- If a problem is present, repair as necessary.
Did you make a repair?
| --
|
Go to Step 16
|
Go to Step 5
|
5
|
- Check the fuel pressure. Refer to
Fuel System Diagnosis
.
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 6
|
6
| Observe the TP 1 signal display on the scan tool while slowly
increasing throttle pedal.
Does the TP 1 signal display steadily increase from about 0.33 volt
at closed throttle to more than 4.0 volts at WOT?
| --
|
Go to Step 7
| Go to
DTC P1220 Throttle Position (TP) Sensor 2 Circuit
|
7
| Monitor
the Long Term Fuel Trim on the scan tool.
Is the Long Term Fuel Trim significantly in the negative range (rich
condition)?
| --
|
Go to Step
8
|
Go to Step 9
|
8
|
- Check the items that can cause the engine to run rich.
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 10
|
9
|
- Check the items that can cause the engine to run lean.
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 10
|
10
|
- Check the primary connections at the ignition coil assembly. Refer
to
Wiring Repairs
in Wirings
Systems for the proper procedure. Also, refer to Checking Terminal Contact
in
Engine Control Module Diagnosis
.
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 11
|
11
|
- Check the ignition coils for any cracks or any carbon tracking.
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 12
|
12
|
- Check the ECM grounds for being clean, tight and in the proper
locations.
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 13
|
13
|
- Check the MAF sensor connections.
- If a problem is present, replace the malfunctioning terminals
as necessary. Refer to
Wiring Repairs
in Wiring Systems for the proper procedure.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 14
|
14
|
- Visually/physically check the vacuum hoses for the following conditions:
• | Routing as shown on the Vehicle Emission Control Information label. |
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 15
|
15
|
- Review all of the diagnostic procedures within this table.
- If all of the procedures have been completed and no malfunctions
have been found, review/inspect the following items:
• | Perform a visual/physical inspection. |
• | All of the electrical connections within a suspected circuit and/or
system |
- If a problem is present, repair as necessary.
Did you find a problem?
| --
|
Go to Step 16
|
Go to Step 3
|
16
| Operate the vehicle under the same conditions (as closely as possible)
as when the original symptom occurred.
Is the original symptom still present?
| --
|
Go to Step 3
|
Go to Step 17
|
17
| Are other driveability symptoms
still present?
| --
| Go to
Symptoms
| System OK
|