2001 VX225 Misses When Idling

[TexasSkeeter]

I'm trying to get a smooth idle. Just had injectors checked and ultrasonically cleaned, cleaned VSP filter, checked regulator (no fuel in vac line), checked plug cap resistance (all were around 4.5 ohms), sync'd the throttle plates, then adjusted the TPS to .51 V at with closed throttle plates (it was at .46V).

Warmed up engine, then I used the tach on the dash to set the idle, but at 750 rpm it wants to quit and won't start unless you "choke" it and/or goose it a little upon firing. So I increased it a little (tach now says about 800 - 850 rpm in gear idling). Now, it doesn't seem to want to quit as bad, but it feels like it has a dead miss when idling in gear; the engine goes, "rump, rump, rump, rump....."

The plugs are newish...maybe 10 hours. It runs great off idle, does 68mph and feels strong. Only at idle does the miss seem to occur.

I understand the VX does NOT cut out cylinders at low speed, so I'm thinking I may have a bad spark situation on 1 or 2 cylinders at low rpm (plugs, wires, coil, etc...).

Before I start pulling plug wires and getting jolted and possibly having a heart attack, falling off the boat and drowning, I thought I would ask for some professional help here. Please reply on the course of action I should take to put the purr in my idle.

Thanks in advance!

[TexasSkeeter]

By the way, I did not have a tps test harness, so I opened the connector plug, attached very small wires to the pink and orange connections, then put the plug back together with the 2 small wires hanging out. I tested voltage across them to adjust tps to .51V. I assume this works. Please advise if not. And yes, I am cheap and impatient.

[rodbolt17]

cheap and impatient typically leads to blown motors.
TPS sets with sutters fully closed and will typically end up around .6V at the correct idle speed.
you are correct that the VX model sparks all 6 at all times.
doesnt matter that your cheap or impatient you still need the correct tooling and meters for the task at hand.
you need to test the MAP,ECT,CKP,O2,knock detect and everything else that modifies spark timing or injection mapping.
handiest tool in my box is a Kv tester.

[TexasSkeeter]

You are right, RodBolt. It's fun learning, but I don't have the tools or knowledge so I'm throwing in the towel and taking it to a qualified mechanic. That's my new problem: finding a good, qualified Yammy OX66 mechanic in the Houston area. Do you have any suggestions? feel free to PM me. Thanks for your help.

[TexasSkeeter]

I took it Texas Marine of Conroe and Robert checked it out for me. Wouldn't you know it, I had overlooked the obvious: 2 LP fuel pumps leaking. I ordered parts and will fix next week. I had assumed that when I replaced one leaker 6 months ago, surely the rest would still be good. Nope. Lesson learned. Hopefully it will idle great when that's done.

Btw, I would recommend Robert at Texas marine in Conroe for you Houston area Yammy owners. He did a good job of checking everything out and going thru the details with me. Seems like a very knowledgable tech with good communication skills.