6E1-90 DRIVEABILITY AND EMISSIONS
Rough, Unstable, or Incorrect Idle, Stalling Symptom (For Open Loop System)
Step Action Value(s) Yes No
DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary
in RPM. Either condition may be severe enough to stall the engine.
1
Was the On-Board Diagnostic (OBD) System Check
performed? -
Go to Step 2
Go to OBD
System
Check
2
1. Perform a bulletin search.
2. 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?
-
Verify Repair Go to Step 3
3
Was a visual/physical check performed, including the
rotor, ignition coil and secondary ignition wires? -
Go to Step 4
Go to
Visual/Physic
al Check
4
1. Check for incorrect idle speed. Ensure that the
following conditions are present.
• Engine fully warm.
• Accessories are OFF.
2. Using a Scan Tool, monitor IAC position.
Is the IAC position within the specified values?
Between 8
and 50
counts Go to Step 7 Go to Step 5
5
1. Visually/Physically inspect for the following conditions:
• Restricted air intake system. Check for a restricted
air filter element, or foreign objects blocking the air
intake system.
• Check for objects blocking the IAC passage or
throttle bore, excessive deposits in the IAC passage
and on the IAC pintle, and excessive deposits in the
throttle bore and on the throttle plate.
• Check for a condition that causes a large vacuum
leak, such as an incorrectly installed or faulty
crankcase ventilation hose/brake booster hose.
Was a problem found?
-
Verify repair Go to Step 6
6
Using a Scan Tool, monitor TP angle with the engine
idling.
Is the TP angle at the specified value and steady?
0% Go to Step 7
Refer to
Diagnostic
Trouble Code
21 for further
diagnosis
7
Check for proper ignition voltage output with the spark
tester (Use commercially available tool).
Was a problem found?
-
Verify repair Go to Step 8
8
1. Remove the spark plugs and check for gas or oil
fouling cracks, wear, improper gap, burned electrodes,
heavy deposits or improper heat range
2. If spark plugs are fouled, the cause of fouling must be
determined before replacing the spark plugs.
Was a problem found?
-
Verify repair Go to Step 9
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