F115 stalling, idling issue

[BigKingy]

Hello,

Engine is a F115 2004 with 441h
Went through a huge service at 404h when I purchased it:
-New fuel filters
-New thermostat, old one was in bad shape
-4 new spark plug (removed one were all carbon fouled)
-New VST
-4 Injectors cleaned by a pro
-Reset the TPS to specs
-Cleaned the ISC

I have intermittent stalling when going back to neutral from cruising and sometime the engine seems to idle not as regular as usual, more like wrom wrom wrom wrom(hard to explain)...
Engine work really well except this issue.

I read all the post of the forums about similar issues maybe 10 times each now.

Some described similar issue due to TPS off specs, ISC sticking, bad shift Switch, damage low pressure pump diaphragm.

What I have done so far:
-on YDS the TPS adjustment is good (0.728V engine off, ignition ON)
-no error code.
-Static test of ISC is good. It also rattle when I turn engine off.
-Active test, 100% request increased RPM.
-During the 30min test, it seems the engine was idling smoother, request was around 65% during all the duration of the test, not sure how to interpret this.
-I did the pressure test as per the book on the low pressure pump and it is good.
-As suggested in another post by Rodbolt, I measured the temp of the ISC after running 5 cycle of stationary test with a IR gun it was 90F. BUT after I left the engine idling for 10min it reach 195F....
On YDS the ISC demand is between 62% and 65% when the engine is idling.

So correct me if I'm wrong but to me it seems the ECU is sending an high request to the ISC. because of this the ISC ends up heating.

When I purchased the engine it was idling really rough as thermostat was not working good and TPS was off. The previous owner might have messed up with the idling screw and/or synchronisation screw. Could this cause the ECU to send an high request to the ISC to correct a bad throttle valve sync?

Should I do a full rest starting with the "ADJUSTING THE THROTTLE
POSITION SENSOR" from the manual?

Cheers

[BigKingy]

Just to double check, does the TPS need to be adjust to 0.732 ± 0.014 V engine running or only ignition ON?

[rodbolt17]

as a pain as it is your going to have to follow the complete procedure starting with the shutters fully closed NOT just at idle.

[BigKingy]

yep, what I thought thanks for the confirmation.

Ok So first I will check the throttle cable adjustment

Second I will follow the procedure "ADJUSTING THE THROTTLE POSITION SENSOR (WHEN DISASSEMBLING OR REPLACING THE THROTTLE BODY"
-Loosen the synchronizing screw and fully open the lower side
throttle valve (#3, 4).
-Loosen the idling screw 1 and fully close the upper side throttle
valve (#1,2).
-Adjust the position of the throttle position sensor until the output
voltage is 0.7 ± 0.01 V and operate the throttle valve several times.
-Record the value.
-Slowly tighten the synchronizing screw 2 until the recorded value is
changed.
-Slowly tighten the idling screw until 0.032 ± 0.004 V increase over
the recorded value.
-Operate the throttle valve several times.
-Install the throttle roller d as the mark e aligns with center of the
throttle roller and check that the output voltage is not change.
-Install the intake silencer.

Third I will start the engine and check the TPS voltage while idling, adjust if necessary (0.732 ±0.014 V)

And last step I will check throttle valve synch and adjust if necessary (vacuum pressure of cylinder #3 or #4 within 30 mmHg of the vacuum pressure of
cylinder #1 or #2)

Does it seems right?

[panasonic]

Follow the manual, make your adjustments and see if it fixes your problem. If not, report your findings and someone will help you out with it.

[BigKingy]

Ok so I end up going in circle today doing the full procedure at least 10 times over and over struggling to get the valves synchronized (I thought I was...).
I figured out late that my homemade synchronization tool has a definition way higher than a classic vacuum gauge. I was used to sync the carbs of my bike perfectly level with this tool but you can try all day on the F115 you will never get the liquid level in the four tube. Cylinder 4 look out of specs on the picture but it is not.



I end up borrowing a vac gauge to double check:

C1:416mmhg
C2:412mmhg
C3:416mmhg
C4:405mmhg

Delta C1-C4 is 11mmhg which is ok according the book.

Engine seems to run better, without load if I open throttle slowly up to 1500RPM it seems to hesitate a bit. I guess I will take the boat for a spin tomorrow to see if it did really help, hard to know on the muf.

ISC is still running hot after 5min idling and is request is still around 65%.

Below the figures I got today after synch with the ISC connected


Then now the figures with ISC disconnected... if I disconnect the ISC and start the engine, the ECU drop to 32%... Is this normal?




Cheers

[BigKingy]

Something half clear in the procedure to reset the synchronization screw and idling screw:

The book says
(6) Loosen the synchronizing screw and fully open the lower side throttle valve (#3, 4).

What do they mean by fully open the lower side throttle valve (#3, 4)? I don't understand how could it be possible to open only #3, 4.... even with the synchronizing screw fully loose, #1, 2 are still moving with #3, 4...

Same thing with the next step:
(7) Loosen the idling screw 1 and fully close the upper side throttle valve (#1,2).

I don't get how you can close only valves #1,2 without closing #3, 4....

Did I miss something?

The way I did it:
I loosened the synchronizing screw and fully opened the 4 valves then I loosened the idling screw and fully closed the 4 valves

[rodbolt17]

you missed a whole bunch.
1&2 sync with 3&4.
there is a bypass air screw in each throttle bore.
You are also missing the fact that the ECU has no idea if the ISC is even bolted to the motor.

[BigKingy]

Thank you Rodbolt! Can you please explain what I am supposed to do exactly?
The manual doesn't mentioned the air screws, not sure how/where to find them ever.
I know the ISC is not talking to the ECU but I don't understand why the request go from 65% to 32% when I unplug the ISC

[rodbolt17]

remember it is a request.
the ECU is monitoring throttle angle(TPS) intake pressure(engine load) and speed.
the ECU then sends a toggled ground path to open or close the ISC(stepper motor).
it does not and cannot physically monitor the valve.
it just looks at speed,load and throttle angle.
do some googleing on open loop speed density EFI.

[pstephens46]

Thank you Rodbolt! Can you please explain what I am supposed to do exactly?
The manual doesn't mentioned the air screws, not sure how/where to find them ever.
[COLOR="Red"]I know the ISC is not talking to the ECU but I don't understand why the request go from 65% to 32% when I unplug the ISC

I think you may be getting caught up in the weeds on this question. Is unplugging ICS and watching the request part of the procedure? The question should be "is 65% normal for idling", correct? Does it matter what the request is when you unplug it?

Having said this, I don't have the service manual in front of me.

In your first post, you described an idling sound that indicated it was unstable. Was the ISC request moving around on YDS when this occurred?

[rodbolt17]

if you will notice the TPS values changed with the ISC unplugged.
most likely a volate issue on the 5Vref.
the request is at 29% cause the engine is now idling higher than the ECU expects and it is trying to lower the idle speed.
however if you unplug any other sensor on that motor it will lock base timing and idle at about 1100 RPM,top speed may or may not be available depending on the sensor.

[BigKingy]

ok cheers guy got it. Rodbolt, my TPS voltage fluctuate every second within the tolerance like 0.722=>0.733=>0.728=>0.744
Is this anormal?

[BigKingy]

Ok so TPS voltage reference is 4.97V

Intake air pressure sensor voltage is 3.35V (measured between black wire and pink/green wire)... should the MAP voltage be 5V too?

When not running MAP shows the same pressure as the atmospheric pressure 29.8inHg
If I unplug the MAP intake pressure is 37.40inHg

[BigKingy]

Tested the boat today, still stalling when going back to idle.
I made a video of the engine monitor:

https://www.youtube.com/watch?v=ctre...ature=youtu.be