TOHATSU BFT75A Service Manual page 123

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TROUBLESHOOTING
ENGINE SPEED DOES NOT STABILIZE WHEN RUNNING AT HIGH SPEED AND ENGINE SPEED IS NOT
AS HIGH AS IT USED TO BE WHEN RUNNING WITH THE THROTTLE FULLY OPEN
1. Throttle link and throttle cable inspection
Inspect the throttle cable (page 3-9).
Is the throttle link and throttle cable adjustment correct?
YES
NO
2. Fuel Flow Inspection
Inspect the fuel flow (page 5-99)
Is the fuel flow within specification?
NO
ENGINE SPEED DOES NOT DECREASE
1. Throttle link and throttle cable inspection
Inspect the throttle cable (page 3-9).
Is the throttle link and throttle cable adjustment correct?
YES
NO
2. Throttle shaft inspection
Check the throttle shaft operates smoothly.
Throttle shaft moves smoothly?
YES
NO
3. Engine idle speed inspection
Check the engine idle speed (page 3-20).
Is the idle speed normal?
YES
NO
4. Intake air leak inspection
Check for secondary air 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
4-10
– GO TO STEP 2.
– Improper throttle link and throttle cable adjustment (page 3-9)
– • Clogged or damaged fuel tube
• Clogged fuel strainer (Low pressure side)
• Clogged water separator
• Clogged fuel strainer (Low pressure side)
• Clogged vapor separator air vent tube or filter
• Faulty vapor separator
• Clogged or damaged fuel feed hose
• Clogged fuel strainer (High pressure side)
• Faulty fuel pump (High pressure side)
– GO TO STEP 2.
– Improper throttle link and throttle cable adjustment (page 3-9).
– GO TO STEP 3.
– Clean or replace the throttle body (page 5-105).
– GO TO STEP 4.
– Improperly adjusted idle adjusting screw.
– • Loose IAC valve and/or throttle body mounting bolt
• Leaking or damaged throttle body and/or IAC valve gasket
• Loose intake manifold mounting bolt
• Leaking or damaged intake manifold seal ring
• Loose fuel line mounting bolts
• Leaking or damaged fuel injector seal ring
– GO TO STEP 5.
– Faulty original IAC valve.
– Replace the ECM with a new one and recheck.