2005 Wakesetter VLX Monsoon 340 Engine Misfire

[b55driver]

I am struggling with this engine miss now since the middle of last season.  The ECU is not talking to the dash.  But I am guessing we have about 800 hours on the engine. 

My problem originally it started out as an occasional miss at high RPM and has gradually degraded to its present state where the miss is consistent above about 2000rpm.

I have found a few problems and fixed them.  But none of them have affected the problem.

Found and fixed: New distributor cap and rotor, new spark plugs.

The fuel pump pressure was high (100+psi) -- new fuel pressure regulator (Although I could have cleaned the old one which had some powder-like black soot. I think it was from abrasion from the fuel filler line during fueling in rough water.) New gas. New fuel filter.  Fuel injectors cleaned myself.  Then fuel injectors sent out for cleaning.  All injectors cleaned, bench tested and check out OK.  Current Fuel pressure is rock solid at 60psi.

That leaves me here.  Spark plug wires are about 8 years old but look to be in good condition.  Coil is original.  Outside appearance is clean.  DIstributor is original and has white powder-like corrosion on the base plate. 

Any suggestions on the next thing to replace?  Distributor, Coil and Wires all together?  Or is there a known soft spot on these engines? It's a new season and I need to get this working!  Thanks for any thoughts.

[minnmarker]

My daughter's Subaru went through the same misfire progression (without all the fixes).  It ran OK but then time came to sell it.  Plug wires looked great and we had replaced the plugs @ 20K miles ago.  Nice guy comes to test drive.  Likes the Sube but complains about misfire.  Talks me down a few hundred.  Goes to get cashiers check.  Comes back with check and new plug wires.  Asks if he can put them in before buying and will leave them in if he doesn't buy.  I say yes.  He puts them in and we go off for a quick drive to check it out.  Engine runs perfect!  He drives away happy.  I learn that nice looking wires are not necessarily good.

[malibuparadise]

Maybe check compression in all the cylinders. That was the cause of my  misfire issue (leading to a head/valve job).  

[Rednucleus]

Replace wires if 8 yrs old - and/or test each wire's resistance with your trusty meter. I, like Minnmarker had wires on my Nissan that looked great. Clean, no cracks, boots in nice shape. 3 of 4 wires were way high on resistance and were responsible for the occasional miss. Also had a bad coil wire that looked great but was shorting under the boot at the coil.

[formulaben]

2 hours ago, b55driver said:

Any suggestions on the next thing to replace?  Distributor, Coil and Wires all together?  Or is there a known soft spot on these engines? It's a new season and I need to get this working!  Thanks for any thoughts.

My 2 cents: absolutely new wires before you even consider a new distributor or coil

[b55driver]

Thanks! new ignition wires on order.  Let's see if this gets it. And while I am ordering, went for a new MMDC. to see if I can get the gauges to start moving again.

[b55driver]

New ignition wires fixed it!  I was distracted for a while with the fuel pressure problems.  But once back on electrical, the wires did the job.  The new wires from Bakes were also a lot higher quality and better fitting than the ones they replaced. Doing the work yourself you know better what is going on the boat.  

Thanks for the comments to confirm the direction.

She purrs like a kitten!

[Rednucleus]

Curious if you checked resistance reading of the old wires. Always am amazed how a perfectly good looking wire is no good when meter checked. Glad you are purring again!