Yamaha F400A 2022 - Page 203

Outboard motor troubleshooting
4-30
Symptom 1: High engine idle speed.
Symptom 1: Engine stalls, unstable engine idle speed, or poor acceleration.
Compression pres-
sure is low
Improper valve timing
Check the valve timing. 7-43
Check the timing belt. 7-43
Check the cam chain. 7-49
Check the chain tensioner. 7-49
Check the VCT for sticking. 7-48
Compression leakage
Check the valve for bends and
sticking.
7-61
Check the piston and piston rings
for damage.
7-77
Check the cylinder for scratches. 7-79
Symptom 2 Cause Checking steps
See
page
—
Air leakage (ETV–cylinder
head)
Check the gaskets of the intake
manifolds, surge tank, and ETV.
6-24
6-28
Symptom 2 Cause Checking steps
See
page
Improper intake cam
timing
Stuck OCV plunger
Check the OCV operation using the
YDIS.
5-25
Check the OCV plunger. 5-25
Clogged OCV filter Replace the OCV filter. 7-58
Clogged oil passage Check the oil passage. 2-49
Stuck VCT Replace the VCT assembly. 7-46
Cam chain wear
Cam chain stretch
Check the cam chain. 7-49
Cam chain tension Check the cam chain tensioner. 7-49
Symptom 2 Cause Checking steps
See
page