What would cause this optimax idle issue?

[jeffadams]

I have a 2010, 175hp regular optimax #1B789623, that has a strange idling issue. When the engine is started, it spits and sputters and occasionally dies. If it dies, I can turn the ignition off and restart the motor and all of a sudden it runs perfectly. How can it go from running so badly to running as smooth as a sewing machine, by just turning the key off and restarting it? What are the things that could cause this?

[JOE54]

you pump bulb before start up ?????

[jeffadams]

Yes, the bulb is always pumped before starting. Pressure remains in the bulb.

[JOE54]

check all connections on engine and batt , look at spark on all 6 and fuel psi when problem is occurring

[EuropeanAM]

One other item: Make sure that the throttle cable is returning the throttle completely and firmly against the IDLE STOP SCREW inside the cowling.

AND make sure that no throttle is applied (EVER) unless the engine is running, in gear and going somewhere.

Any variation of these items can cause really weird idle performance OR even faults.

[jeffadams]

Thanks Don. I did check the idle stop screw gap and it checked out with the piece of paper test. What I don't understand is that the motor is missing at idle and when I shut it down and restart, everything runs fine....no misses or sputtering. Why would the motor all of a sudden run fine after restarting it?

[lpugh]

check for voltage drop across the master power relay for good starting place, disconnect and reconnect the engine harness connector and inspect the pins

[JOE54]

^^^^^^+1

[EuropeanAM]

Since you used the "piece of paper test" can we confirm you are using a HAND THROTTLE (and not a hotfoot)?

[jeffadams]

Yes, I do have a hand throttle and not a hotfoot. All linkage is in good shape, and I did replace the roller on the throttle cam recently. I checked the engine harness and cleaned the multipin connector with contact cleaner. The connection seems good and tight. I also cleaned all of the coil posts and found 3 that were pretty dirty, especially the two bottom coil posts. Will try and run the engine in the next few days.