f-115 misfires at lower rpm

[L4Rosales]

I have a 2005 f-115 with 440 hrs on it. It is running poorly at low rpm (below approx 3800rpm) and when cold, but runs almost like it should at higher rpm (down to 5400rpm with lighter load compared to 5900rpm with heavier load). Engine also idles fine. When I ran the boat with a new plug, it ran better at higher rpm (got up to max 5800rpm with light load and performance was marked improved while engine was cold).

I ran a scan after 439hrs using my recently acquired ydis. The only codes listed were h2o sensor at 0.3hrs, shift position switch 108.1 hrs, pulser coil 385.4 hrs. I deleted all codes and installed a new plug (#4 plug has carbon buildup) and ran the motor again and one code showed up: Shift position switch 440.9 hrs. (I didn’t run the engine with the laptop hooked up).

Yesterday, I was able to run the boat with the laptop hooked up. I am including the test results, hoping for some advice. I also am including fuel pressure readings at selected rpm.

RPM Fuel Press (psi) Comment:
0 Initial scan before running the boat.
898 36 Idle (cold). I was going to take a
snapshot when warm also, but forgot.
Engine ran smooth at idle.
2048 40 Fuel pressure "pulsed" when engine misfired,
but otherwise constant. pulse approx 1-2
psi and only noticeable at lower rpms.
2597 42
3000 43
3554 43+
4214 Engine ran without noticeable missing.
(engine began to run smoother at approx
3800 rpm and sounded very good at 4200)

After running the tests, I ran the boat for another hour or so, but did not run a scan afterward.

I put all of the tests on one excel sheet and am attaching the results. I deleted all of the duplicate info and only left data that was not constant. I am still very new to this ydis and don't really know what I am looking at right now.

Thank you for any help and advice,
Louis

[rodbolt17]

would like to see a full screen snapshot of the engine paremeters when running.
looking at min 4 notice the sudden dip in engine temp?
looking at the TPS v at 4050 it almost looks like your running with no load yet the intake pressure shows almost full throttle opening.

the shift position switch can cause funny things if its not working or the wiring to the ECU is damaged.

switch can be easily monitored on the YDS simply by on(N) or off in F or R.

looking at key off baro information your either inland at a higher elevation than our coast or the weather is starting to suck.

looking at the key on engine off intake air at least its warm outside.
looking at the temp when running you never got the cooling system warm enough to operate the T stat or the t stat is defective.

typically the YDS simply tells me where I don't have to look but its great for spotting inrange sensor failures and anomalies.

[L4Rosales]

would like to see a full screen snapshot of the engine paremeters when running.
looking at min 4 notice the sudden dip in engine temp?
looking at the TPS v at 4050 it almost looks like your running with no load yet the intake pressure shows almost full throttle opening.

the shift position switch can cause funny things if its not working or the wiring to the ECU is damaged.

switch can be easily monitored on the YDS simply by on(N) or off in F or R.

looking at key off baro information your either inland at a higher elevation than our coast or the weather is starting to suck.

looking at the key on engine off intake air at least its warm outside.
looking at the temp when running you never got the cooling system warm enough to operate the T stat or the t stat is defective.

typically the YDS simply tells me where I don't have to look but its great for spotting inrange sensor failures and anomalies.

How do you take a whole page snapshot while running? I just used the "engine monitor" while running and assumed that was it. What else is there that I could do?

I hadn't really looked at the temp difference, it is probably because I shut the motor down for a few minutes before coming into the ramp the last time out before that scan?

What is the tps voltage I should be seeing while under load and throttled up? closer to 4?

I will experiment a bit more with the yds to monitor and take a snapshot of the switch position switch.

I'm on the left coast, and the weather has been really nice. Hope you get a red sky at night.

The engine had been running for long enough to get up to temperature. I guess I'll have to look at the t-stat.

[L4Rosales]

What is the temperature range that an F115 should be running at after coming up to temperature?
thanks,
Louis