Troubleshooting Guide — 14 Idle Moves Up and Down/Idle Hunting
F2-43flowchart14 IDLE MOVES UP AND DOWN/IDLE HUNTING
DESCRIPTION: Engine speeds up and down at idle
NOTE
[TROUBLESHOOTING HINTS]
1. Closed throttle position switch (built-in throttle position sensor) OFF at idle
2. Air leakage
3. Fuel injection amount inconstant
• Poor contact point inside volume air flow sensor
4. Poor ignition
14 Idle Moves Up and Down/Idle Hunting
1
STEP 1: Is "00" displayed on SST with ignition switch ON? (page F2-73)
No
Diagnostic trouble code No. displayed — Check for cause (Refer to specified check sequence) (page F2-74)
Yes
2
"00" displayed — Go to next step
3
STEP 2: Is intake manifold vacuum correct at idle? Intake manifold vacuum: More than 450 mmHg {17.7 inHg}
No
Low vacuum — Check for air leakage of intake-air system components
Yes
4
Go to next step
5
STEP 3: Is air cleaner element clean? (page F2-70)
No
Replace air cleaner element
Yes
6
Go to next step
7
STEP 4: Disconnect high-tension lead at idle; does engine speed decrease equally at each cylinder?
No
Go to step 8
Yes
8
Go to next step
9
STEP 5: Are ECM terminal voltage OK? 1C-Starter signal; 2E-Engine coolant temperature sensor; 3D-Sensor ground (page F2-141)
No
Check for cause (page F2-141)
Yes
10
Go to next step
11
STEP 6: Connect System Selector to data link connector and set Test Switch to "SELF TEST"; is ignition timing at idle correct after warm-up? (page F2-70) Ignition timing (BTDC): 9—11° {10 ± 1°}
No
Adjust ignition timing (page F2-70)
Yes
12
Go to next step