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Mercury Optimax 225 DFI : IDLE PROBLEM

laurent

New member
I encounter a problem on my Mercury 225 hp.
Idle is unstable.
the engine starts badly at 4000 rpm, it goes down to 3500 rpm then goes back to 4000 rpm .......
Fuel pressure : 90psi
Air Pressure : 80psi

I don.t understand.!!!!
Can you help me ?

Sorry for the translation
I.m French.
 
Check the wire connectors at each temperature sensor for corrosion. A wandering engine idle can be caused by a loss of temperature readings which confuses the engine computer because it does not know the temperature of the air or engine block.

PS: Your english is easily understood.
 
Thank you so much !
I will immediately check all engine temperature sensors.
How many sensors on the engine? Four?
What is the role of each?
 
My Merc. manual is for 150 HP and under but I assume the electronics are similar. Use the engine serial number to search above in Merc. outboard parts schematics to see how many and where the sensors are located.
 
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