TOHATSU BFT115A Service Manual page 102

TROUBLESHOOTING
ENGINE SPEED INCREASES EXCESSIVELY
1. Propeller inspection
Check the propeller for bend or damage.
Is the propeller normal?
YES
NO
2. Outboard motor installation inspection
Inspect the outboard motor installation (Transom height/tilt angle).
Is the outboard motor installed correctly?
NO
ENGINE SPEED DOES NOT DECREASE
1. Throttle link/ control cable inspection
Inspect the throttle link/control cables (page 3-9).
Is the adjustment correct?
YES
NO
2. Throttle body inspection
Check the throttle shaft of the throttle body.
Does the throttle shaft move smoothly?
YES
NO
3. Engine idle speed inspection
Adjust by turning the idle adjusting screw (page 3-13).
Does the engine speed decrease?
YES
NO
4. Intake air leak inspection
Check for secondary air leak between the silencer case and cylinder head.
Is there an air leak?
YES
NO
5. IAC valve inspection
Replace the IAC valve with a new one and start the engine.
Is the engine idle/trolling speed normal?
YES
NO
4-12
– GO TO STEP 2.
– • Propeller mismatched
• Faulty propeller
– Faulty outboard motor installation.
– GO TO STEP 2.
– Improper throttle cable adjustment (page 3-9).
– GO TO STEP 3.
– Check the throttle body and clean it (page 5-136).
– Improper original idle adjusting screw adjustment.
– GO TO STEP 4.
– • Loose IAC valve and/or throttle body mounting bolt
• Leaking or damaged throttle body and/or IAC valve gasket
• Loose IAT sensor
• Leaking or damaged IAT sensor O-ring
• Loose intake manifold and/or injector base mounting bolt
• Leaking or damaged intake manifold gasket
• Leaking or damaged injector base gasket
• Leaking or damaged fuel injector seal ring
– GO TO STEP 5.
– Faulty original IAC valve
– Replace the ECM with a new one and recheck.