04 yamaha 4 stroke vibrate stalls at idle

[rudderz71]

Hey guys!
I had a local marina service my engines this summer and they changed my spark plugs. I picked the boat up after and the starboard engine runs great as always, but the port engine was rough and missing. Turned out they crossed the spark plug wires hooking them back up. I put about 2 hours on the boat when the wires were crossed and then pulled it to inspect the issue. I replaced the spark plugs on the port side of the block cylinders 2, 4, 6 and put the wires back the way they belong. Boat ran much better but still not seeing 6000 rpm, (saw 5700) and the boat stalls and vibrates at low rpms or idle. Pulled the 3 plugs for re inspection, and 4, 6, are pretty, and number 2 looks a little black and rough. fuel pressure is 4100 at the rail. Please help!! I am thinking electrical thanks guys!!

[99yam40]

Hey guys!
I had a local marina service my engines this summer and they changed my spark plugs. I picked the boat up after and the starboard engine runs great as always, but the port engine was rough and missing. Turned out they crossed the spark plug wires hooking them back up. I put about 2 hours on the boat when the wires were crossed and then pulled it to inspect the issue. I replaced the spark plugs on the port side of the block cylinders 2, 4, 6 and put the wires back the way they belong. Boat ran much better but still not seeing 6000 rpm, (saw 5700) and the boat stalls and vibrates at low rpms or idle. Pulled the 3 plugs for re inspection, and 4, 6, are pretty, and number 2 looks a little black and rough. fuel pressure is 4100 at the rail. Please help!! I am thinking electrical thanks guys!!

I do not think a 4 stroke should have 4100 psi on the rail.

What motor do you have

I would have a leak down test run as firing at the wrong time could cause problems in the motor

[rudderz71]

its a 2004 yamaha f225 4 stroke
41 psi at the rail sorry typo. Do you think the internal air control could have been back fired through causing it to fail?

[99yam40]

I was thinking more on the line of valves, stuff that seal the cylinders

[rudderz71]

ok will perform the leak down test.
again engine has hit 5700 rpms and runs great after 1200 rpms
spark plugs 4 and 6 look great after 20 mins of running plug 2 looks more aged even though all 3 are new

[Colemac53]

It sounds like you could possibly have an injector that is stuck open causing the spark plug to fowl out and cause it to miss fire

[rudderz71]

i think the injectors could be factored out with a 5800 rpms and 41 psi at the rail ?
seems as if the IAC is fowling that plug and killing the idle

[rudderz71]

update...
Mechanic said he tested IAC on computer and didnt find anything. Im kinda lost at this point engine runs great just cant figure out why cylinder 2 is not functioning, and the engine stalls at idle? Any help would be greatly appreciated

[greasyshaft]

Check compression(leak tests are better) and spark on that cylinder What revs did the engine get before the service?
What is fuel pressure at the rail when the problem is occurring? if the engine is stalling at low rpms the infamous check valve could be a problem.

Try swapping plugs/injectors/ignition coils around see if the problem moves

no. 2cyl and 5cyl are grouped for injection and spark

[rodbolt17]

my guess would be fuel.
however a quick test with the laptop can rule out a bunch of bunnies.

[rudderz71]

Engine ran great last fall/winter. Boat was serviced and stored away for winter months
Spark plug wires were crossed when the mechanic changed the plugs. I have to believe this is a direct issue being that the starboard engine runs so great. I always run tanks to almost empty then fill up before i drop in the spring. 200 fresh gallons this year. I still suspect the IAS but not sure how you can test that and or maybe a fouled injector at number 2. Guy is really killing me.

[rodbolt17]

dude.
the spark plugs fire in pairs.
if one of the coil wires spark the other does at the same time.
that's why there are 3 coils to spark 6 cylinders.
mixing them up wont affect anything other than the engine wont run correctly until they are back in the correct order.

storage does funny things.
typically that's when fuel systems degrade.
that's why a quick check with the laptop will prevent you from chasing ghosts and hunting wabbits.
BTW, the ISC(IAC) valve controls idle air to ALL 6 cyl.

[greasyshaft]

there is a test on yds for the isc valve. basically you press enter and the isc valve opening request is set to 100% if the isc valve is functioning correctly revs should increase I would doubt it is your prob

[99yam40]

You rule out stuff without even checking

adding fresh fuel to old can get you more bad fuel, not keeping air out of tanks can cause more condensation/ water to form in tank over the off season

seems you do not want to take anyone's recommendations, so why should we keep trying to give any

[rudderz71]

Thanks so much for the responses and yes I am trying to take advice. A lot of the things that you folks have advised have been done. Possibly fuel or injector at this juncture. I am just trying to gain some direction on where to go. Computer is not saying anything as I assumed due to no alarm. I have replaced,cleaned the VST and F filter. All new filters look good. Compression is even on all cylinders, and the pressure at the rail is where it should be. Just searching here. Starboard engine runs flawless. Boat used to see 6000 rpms at wot and now its only hitting 5800 with vibration and no idle. Cylinder 2 is fouling plugs that is all I know!