2006 F90 misses about 2600-3700 RPM's

[kajikikai]

HI all, I got a 2006 F90 fuel injected outboard. Motor misses around 2600-3700 RPM's. Anything above or below runs fine. Does not seem to miss after boat is on plane. Cleaned the VST & screens at the injectors. Changed the spark plugs and wires. Did not have the injectors cleaned. Only Non ethonol fuel is run. Hope you guys can help.

Thanks in avance,
Kajikikai

[99yam40]

You will need to test things to see if it is loosing spark or maybe fuel related.

Has that motor been hooked to any testing equipment or are you just throwing parts at it and hoping?

[kajikikai]

No it has not been hooked up to the tester. I bought it but couldnt get it to work. Seems like the problem started after changing the regulator / retifier because of overcharging. was showing 17 volts now 15 volts.

[greasyshaft]

Why did you change the VST filter? was it clogged?

If you had crap at the injectors you need to have them tested for correct spray pattern.

You have to monitor things at the problem Rpm in order to get anywhere, having her plugged into YDS (by someone who knows what they are looking at) would be a start.

That engine Groups 1-4 and 2-3 for ignition and fuel injection.

[bajakeith]

Jeez

YDS is not GOD !! this type of issue could be from a hull//prop//load///and a host of electrical issues !! broken/loose flywheel magnets to a bad ignition swith that vibrates at those RPMs...and also a bad Tach..O,,Before ya start giving the guy a bad time.....

[greasyshaft]

No shit, maybe a dark wizard put a spell on his boat. I wasn't giving him a hard time at all.

[kajikikai]

I didn't change the VST filter just cleaned it. Both VST filter & injector screens were pretty clean. Boat was running fine before the high voltage so I don't think its anything with the boat or props. Noticed the high voltage and came in within 10 minutes. I'll prob get someone to look at it. Was just wondering if anyone had or ran into similar problems. Thanks

[rodbolt17]

only thing the flywheel has to do with ign on that engine is to trigger the pulser coils.
the ign system is a 12V TCI type.

[kajikikai]

So I had a guy come and look at the motor, he hooked up a timing light and inspected the spark. seems like the #2 & #3 cylinders had an erratic spark. The #1 & #4 spark was pretty consistent. The motor idles at 650 rpm's. What sends the signal to the ignition coils?

[rodbolt17]

like I tried to explain, its a waste spark TCI system.
it has NO signals sent.
at key on the system is powered by 12v DC.
a set of transistors located in the ECU shut off the current based on pulser coil signals.

its not anything like the old CDI setups.

TCI uses 12v and the ground path is the ECU,when the transistor shuts off current stops flowing,the magnetic field in the ign coil primary collapses and a voltage is induced in the secondary winding.

its a solid state version of points and condenser

[kajikikai]

like I tried to explain, its a waste spark TCI system.
it has NO signals sent.
at key on the system is powered by 12v DC.
a set of transistors located in the ECU shut off the current based on pulser coil signals.

its not anything like the old CDI setups.

TCI uses 12v and the ground path is the ECU,when the transistor shuts off current stops flowing,the magnetic field in the ign coil primary collapses and a voltage is induced in the secondary winding.

its a solid state version of points and condenser

Thanks for the reply.
So that being said, my ECU is bad? Sorry Mr. rodbolt, I'm just trying to fix this motor. From where I live, you really dont have too many choices on where to take your Yamaha, I think 2. And all I hear is horror stories when talking to other boaters about the services they received.

[arny]

would try to swap ign.coils to see if trouble follows coil.

[kajikikai]

Will do. Thanks for the advice! Let you guys know how it turns out!

[99yam40]

Make sure your pulser coil signals are good before replacing anything else

[kajikikai]

Hi gang,

Just a heads up on whats going on...well I swapped the coils and seems like the spark is a lot more consistent on BOTH coils now. Not sure why, possibly a bad connection. I'm crossing my fingers that thats the problem, but only a test ride would confirm this and probably wont be getting into the water till Sunday. And yes Ill check the pulser coil before replacing anything. Thanks for all your replies / help. I'll keep you guys posted on the outcome!