Hesitation, Sag, Stumble Symptom
Step
| Action
| Value(s)
| Yes
| No
|
DEFINITION: Momentary lack of response as
the accelerator is pushed down Can occur at any vehicle speed Usually most
pronounced when first trying to make the vehicle move, as from a stop sign
May cause the engine to stall if severe enough.
|
1
| Was the Powertrain On-Board Diagnostic
(OBD) System Check performed?
|
|
Go to Step 2
| Go to the
Powertrain On Board Diagnostic (OBD) System Check
|
2
|
- Perform a bulletin search.
- If a bulletin that addresses the symptom is found, correct the
condition as instructed in the bulletin.
Was a bulletin found that addresses the symptom?
|
|
Go to Step 21
|
Go to Step 3
|
3
| Was visual/physical check performed?
|
|
Go to Step 4
| Go to
Visual/Physical Checks
|
4
|
- Check Heated Oxygen Sensors (HO2S). The Heated Oxygen Sensors
(HO2S) should respond quickly to different throttle position. If they don't,
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 in a high but false HO2S signal voltage (rich exhaust indication).
The PCM will then reduce the amount of fuel delivered to the engine , causing
a severe driveability problem. Refer to
Information Sensors
.
- If a problem is found, repair as necessary.
Was a repair required?
|
|
Go to Step 21
|
Go to Step 5
|
5
|
- Check the fuel pressure. Refer to
Fuel System Pressure Test
.
- .If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 6
|
6
| Observe TP angle display on the scan tool while slowly increasing throttle
pedal.
Does the TP angle display steadily increase from 0% at closed throttle
to 100% at WOT?
|
|
Go to Step 7
|
Go to Step 20
|
7
| Monitor Long Term Fuel Trim on the scan tool.
Is Long Term Fuel Trim significantly in the negative range (Rich condition)?
|
|
Go to Step 8
|
Go to Step 9
|
8
|
- Check items that can cause the engine to run rich. Refer to
DTC P0172 Fuel Trim System Rich
.
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
| --
|
9
|
- Check items that can cause the engine to run lean. Refer to
DTC P0171 Fuel Trim System Lean
.
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 10
|
10
|
- Check for proper ignition coil output voltage with spark tester J 26792
:
- | Clip the spark tester to engine ground. |
- | Connect one end of a spark plug wire to the spark tester; connect
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 all coils, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 11
|
11
|
- Check for loose ignition control module ground.
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 12
|
12
|
- Visually/Physically inspect secondary ignition wires. Check for
the following conditions:
• | Check all ignition wire resistances; should be less than the specified
value. |
• | Ignition wires for cross firing. |
• | Ignition wires arcing to ground. |
• | Ignition wires for improper routing. |
| 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.
|
- If a problem is found, repair as necessary.
Was a problem found?
| 30K ohms(30,000 ohms)
|
Go to Step 21
|
Go to Step 13
|
13
|
- Check ignition coils for cracks or carbon tracking.
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 14
|
14
|
- Check ignition coil secondary resistance.
- Replace any coil(s) which are not within the specified values.
Refer to
Ignition Coil
.
Did any coil(s) require replacement?
| 5K-8K ohms(5000-8000 ohms)
|
Go to Step 21
|
Go to Step 15
|
15
|
- Remove spark plugs and check for wet plugs, cracks, wear, improper
gap, burned electrodes, or heavy deposits.
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 16
|
16
|
- Check PCM grounds for being clean, tight and in the proper locations
Refer to
Engine Controls Schematics
.
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 17
|
17
|
- Check MAF sensor connections.
- If a problem is found, replace faulty terminals as necessary.
Refer to Electrical Diagnosis for wiring repair procedures.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 18
|
18
|
- Visually/physically check vacuum hoses for splits, kinks, and
proper connections and routing. Refer to
Emission Hose Routing Diagram
.
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
|
Go to Step 19
|
19
|
- Review all diagnostic procedures within this table.
- If all procedures have been completed and no malfunctions have
been found, review/inspect the following:
• | Visual/physical inspection. |
• | Freeze Frame data/Failure Records Data. |
• | All electrical connections within a suspected circuit and/or system. |
- If a problem is found, repair as necessary.
Was a problem found?
|
|
Go to Step 21
| Refer to Technical Service Bulletins
|
20
| Replace the TP sensor.
Refer to
Throttle Position Sensor Replacement
.
Is Action complete?
|
|
Go to Step 21
|
|
21
| Operate the vehicle to duplicate conditions
present when the original symptom was noted.
Is symptom still present?
|
|
Go to Step 3
| System OK
|