Fuel injectors - what issues do they cause?

[frosh coach]

I'm trying to expand my knowledge on fuel injectors. I have a 350 MPI (2000) that after a long run (2.5 hours) seems to be off a bit at an idle.

So far we have changed plugs, wires, cap, rotor, and fuel filters. I'm starting to wonder if maybe an injector(s) is dirty/clogged.

The boat runs great on above 1100 rpm, and when cursing (3100).

Thanks
Chris

 

[ttmott]

Typically, Idle issues on FI engines center around the Idle Air Control (IAC) valve. Some Mercury configurations have a little foam filter they call a muffler covering the IAC air inlet that gets plugged up and needs to be replaced. The IAC which is controlled by the engine management system, throttles the amount of air that enters the engine at idle and thus controls the idle RPM. If the foam muffler is gone the IAC can get dirty and not function properly and needs to be taken off the throttle body and cleaned.

 

[frosh coach]

Typically, Idle issues on FI engines center around the Idle Air Control (IAC) valve. Some Mercury configurations have a little foam filter they call a muffler covering the IAC air inlet that gets plugged up and needs to be replaced. The IAC which is controlled by the engine management system, throttles the amount of air that enters the engine at idle and thus controls the idle RPM. If the foam muffler is gone the IAC can get dirty and not function properly and needs to be taken off the throttle body and cleaned.

Thanks, I'll check it out.

 

[frosh coach]

Thanks, I'll check it out.

Update on this. After the full tune-up, did a compression test... Well, 60 PSI on on cyc meant a head job. Since we had the motor apart, I sent all 16 injectors (both engines) out to be cleaned. I'm a happy boater again.