off idle rough run

[lpugh]

1B492184 250 pro xs
Idle to 1000 rpm is perfect at 1500 rpm back normal all the up to top speed at 5850 rpm. 1100 to 1400 very rough, feels like random misfires.
Does not do this in neutral.
Owner said this has been an issue for 2 years, occasionally clears and runs normal.
This motor has been apart before, and many things noticed that make me question their skill and knowledge.

Due to a compressor failure and things noticed the following is what has been done:
No faults in run history.
Powerhead gasket (water leak)
new compressor
Injectors flowed and cleaned (5 direct injector replaced)
Air pressure and fuel pressure diaphragm's replaced,
Spark Plugs 1ZFR6J .044 GAP
Throttle cam roller replaced (flat spot) gap .010.
throttle plate set to .145 total, .093 high side.
compression test 115-120
Pressures 94 & 109 spread 15PSI a touch on the high side, virtually no leak down
TPS sweep test with scanner and DSO are perfect.
Stress tested coils with scan tool, all bridged a .600 plus air gap.
Belt tensioner 80 in lbs to stop.
There is a case leak on the port side halfway up. I have seen this before and never noticed running issue because of it.

Map sensor was replaced 2 years ago in attempt to resolve this by someone else.

I think it is time inspect the reeds. but wondering if when the previous motor work was done if maybe it could have a tunner mismatch.

Whats yout thoughts on this?
​ dis

[FeFanatic]

I know you tested the coils but is it possible that a couple could be snapping to ground internally after warmed up? Not in marine environments but in automotive environment I have seen coils work in open air and fail when spark plugs are under compression. It takes more spark to fire under compression.

[JOE54]

inspect reed /are they the original carbon fiber????

[EuropeanAM]

Check the throttle roller for flat-spots. Was fairly common back in that time period.

Also be good to know if they used OEM diaphragms or Aftermarket. The valves in the aftermarket ones are "uber-stiff".

BTW... that particular RPM range has just enough time spent on it (900-1450 RPM's) to make sure it remained running. Never intended to be "smooth" since seldom ever were they run for extended periods pushing water that hard.

[lpugh]

inspect reed /are they the original carbon fiber????

I dont know or trust the work done by the previous tech, thinking reed inspection will be next.

[lpugh]

Check the throttle roller for flat-spots. Was fairly common back in that time period.

Also be good to know if they used OEM diaphragms or Aftermarket. The valves in the aftermarket ones are "uber-stiff".

BTW... that particular RPM range has just enough time spent on it (900-1450 RPM's) to make sure it remained running. Never intended to be "smooth" since seldom ever were they run for extended periods pushing water that hard.

Rollor is new, This is considerably more than what is normal for these motors, I do know what you are refering to.

[EuropeanAM]

Leon- I've had just one engine that did what you're describing. Subsequently performed wide-range of tests on direct and fuel injectors and eventually found one (1) fuel injector that would intermittently drop out intermittently. RPM in testing was about 400-600 RPM's above where the engine experienced it, but was quite noticeable when present.

Replaced that one injector and it ran quite happy after that.


Don't see this much anymore, but make sure you don't have a yellow plastic cap hung in a reed block.

[lpugh]

Well I missed this one, throttle lever was very loose on the shaft, tps would be almost 50% before throttle blade moved, can't believe I missed that one when I replaced the roller, simple stuff can really bite you sometimes, OUCH!
Started to pull the air handle for reed inspection and noticed this instantly. It would still open the blade to wot position.
New lever kit took care of that, never have I seen one wallowed out so bad. The hole for the retention screw was at least 1/4 long.

[Savage]

Yikes....motor saw alot of throttle modulation. Mine is mostly WOT, with small mix of idle lol

[JOE54]

Well I missed this one, throttle lever was very loose on the shaft, tps would be almost 50% before throttle blade moved, can't believe I missed that one when I replaced the roller, simple stuff can really bite you sometimes, OUCH!
Started to pull the air handle for reed inspection and noticed this instantly. It would still open the blade to wot position.
New lever kit took care of that, never have I seen one wallowed out so bad. The hole for the retention screw was at least 1/4 long.

good lord, how many hrs on that engine

[lpugh]

Computer show a little over 900 hrs, very suspicious of a mixed bag of parts on this one

[EuropeanAM]

Quite possible. There's one company in particular that was known for doing that kind of stuff under previous management.