1999 SX200TX - No Power

[99yam40]

needs to suck thru the intake valves while they are open , and the exhaust valves are closed

[tsheehy]

I checked to make sure the thermo-sensor was operating correctly today - as it is one of two sensors that could fail and not have a code show up on diagnostic lamp.

Sensor was right on spec through the various temp ranges in the shop manual.

What am I missing?

If engine was in some form of RPM reduction mode, I would be hearing an alarm or at least getting a code on the diagnostic light, right?

What else am I missing?

-- Tom

[scofflaw]

Runs good, then doesn't , then good again. Have you checked for a bad wire ? How's your voltage when this happens ? I see RB hasn't seen your thread yet, he might save your ass. There's some knowledgeable OX guys over at THT

[tsheehy]

Updated list of troubleshooting steps taken below:
x Both batteries are brand new and otherwise seem to be fine. Voltage readings on gauges/electronics appear to be normal, no sign of low voltage conditions which would ordinarily reset my electronics (fishfinder/gps).
x Both low pressure fuel pumps were replaced in the spring.
x VST filter was inspected/cleaned in the spring.
x Engine is still pissing ok.
x Mechanical linkages seem ok, nothing seems broken or out of place. Both gear and throttle linkages appear to be adjusted correctly and binnacle controls move smoothly when linkages are disconnected from the engine.
x Compression check seems OK, getting 130 PSI across top and bottom cylinders, 135 PSI across middle.
x Validated proper operation of thermo sensor under a range of temps per the shop manual.
x I get no codes on the winky blinky, both when idling and when the problem is occurring at higher RPMs.
x Fuel pressure out of the VST remains constant at ~35 PSI, even while the problem is occurring at higher RPMs.
x TPS voltages check out ok, and appear to be behaving correctly when throttle is adjusted, even while problem is occurring.
x Tried a new set of spark plugs. Verified that all plugs are firing with an in-line spark plug tester.
x Validated spark plug end cap resistance was in spec.
x Checked O2 sensor and joint, both visually and with multi-meter and all appeared ok.

Trouble conditions:
x Idle RPMs have increased to 1000-1200 RPM with boat in neutral.
x Engine sounds rougher than usual - RPMs appear to be limited to a certain point, approximately 2200 RPM. Very infrequently the engine will rev up to 'catch up' with where I have moved the throttle, increasing or decreasing throttle by a couple hundred RPM.
x No codes on the diagnostic light (winky blinky) - no audible alarms.
x Engine struggles to provide any power above idle.
x At one point early on I was able to 'reset' out of the problem condition, get the boat up on plane and zip around like nothing had changed. Brought back to idle/neutral and problem resurfaced. Got it to reset a while later, but while up on plane the engine dropped RPMs quickly a few times which is when I headed back to the dock.
x During last test, noticed a bit of fuel/oil mix coming up through exhaust - not sure if this is due to my futzing or another indicator of problem that I hadn't noticed before or is getting worse.

Things I haven't tried:
x Removing/inspecting/testing the fuel injectors
x Any testing around the ignition system and/or CDI. I don't have a DVA or adapter for my multi-meter.

Anything else you guys can come up with?

-- Tom

[99yam40]

what is rail pressure both normal and during problem.
what is timing doing
what about the 5 volts reference voltage to the sensors, is it being drawn down when problem shows up?

[rodbolt17]

at the high idle speed what is the ign timing?