TOHATSU BFT250A Service Manual page 106

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TROUBLESHOOTING
ENGINE SPEED DOES NOT DECREASE
1. Throttle cable inspection
Inspect the throttle cable (page 3-11).
Is the throttle cable 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
Check the idle speed (page 3-22).
Is the idle speed normal?
YES
NO
4. Intake air leak inspection
Check for a secondary air leak in the system.
Is there an air leak?
YES
NO
5. IAC valve inspection
Replace the IAC valve with a new one and start the engine.
Does the engine speed decrease?
YES
NO
4-14
– GO TO STEP 2.
– Improper throttle cable adjustment (page 3-11).
– GO TO STEP 3.
– Check the throttle body and clean it (page 5-117).
– Improperly adjusted idle adjusting screw.
– 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 upper cover mounting bolt
• Leaking or damaged intake manifold upper cover seal ring
• Leaking or damaged intake manifold gasket
• Leaking or damaged injector base gasket
• Loose intake manifold and injector base mounting bolt
• Leaking or damaged fuel injector seal ring
– GO TO STEP 5.
– Faulty original IAC valve.
– Replace the ECM with a new one and recheck.