Engine stumble/hesitation - 7.4 mpi

[kilroy]

Re-post from '99-'04 260 thread...

This has happened three times now in the last couple of weeks. At no-wake speed (the channel in/out of our marina requires no-wake for 10-12 minutes each way) the engine will stumble or hesitate and then catch itself. Rpms will drop and recover (so quickly that tach barely recognizes the change) and then all will be fine. Bought the boat late last summer and plugs were installed at the time but not the wires/rotor, all of which are likely original. At speed everything is fine. Thoughts?​

 

[osubob]

I troubleshooted the exact same thing. It ended up being the Ignition Control Module. I found this out after replacing Plugs, Wires, Cap, Rotor, Pickup, coil, and Knock Sensor.

Bob

 

[kilroy]

Was some kind of diagnostic performed to determine that it was the module?

 

[osubob]

No. Best way is to swap them between the engines and see if the problem follows. I ended up replacing it since I had an old ICM on one engine and a newer one on the other. They could not be swapped. I replaced it and it did the trick. Runs like a top now.