ISC valve replace?

[jackmanjls]

The F90TLR runs rough or stalls at idle.

I posted a thread about this ISC valve about 1 week ago. When I close this thread out will reference the other thread for future documentation.

Using YDS 1.33 on my F90TLR I ran the Stationary (ST) and Active(AT) tests.

Part of the ST is the 'Operate ISC valve'. From what I gather the valve range is suppose to be between 0% and 100%. I saw up to 70%, didn't record the low %. I did hear the valve stepping when testing. In all cases I didn't hear the stepping(rattling) when turning the motor, I listened closely. At this point, I have evidence that the ECU, ISC wiring and the step circuitry in the ISC valve are functional.

For the 'Active test' I did the 'Fully Open ISC' and found the YDS displayed from 12% to 100%. For the 'Angle of ISC value opening' the test started with the ISC valve opening at 60% and by the end of the test it was 0%. Part of the process of this test is to adjust the angle of ISC valve, my service manual doesn't say anything about how to adjust this.

All other parameters/test using the YDS were within specs.

During my testing, ~ 2hrs, I started/stopped the motor several times. About 50% of the time it ran normal and the other 50 abnormal (rough/stalling idle). When it did run abnormal I shutdown and immediately ran the ST-Operate ISC valve which pulses the ISC and displays the results. In all cases, immediately following I would start the motor and it ran smoothly.

Based on the above paragraph my conclusion is that the ISC valve is intermittent but am reluctant to make the plunge for a new valve until I get some feedback.

Here's my q's.
1. based on the experience in this forum is my initial analysis flawed or am I on the right track?
2. are there any additonal tests I can do to verify the ISC is defective?
3. is it possible to have an interrmitent ISC?
4. can the ISC be cleaned/soaked?
5. how is the angle of the ISC adjusted and is it critical in this situation?

[rodbolt17]

to many questions we cant answer.
can you clean/soak it? yep.
will it work? dunno.
use a temp gun and check on the temp of the valve.
anything over about 210*F means the valve is failing.

really don't carew what the ECU displays during testing.
its irrelavent and meaningless as its simply a request and doent mean the valve actually moved.
what your looking for is did the idle speed increase with a larger % request and decrease with a smaller request.

member dude.
the ECU simply does NOT monitor the ISC.
it toggles the ground path of the ISC stepper motor and assumes it moves.
now if it does NOT move the ECU will continue toggling the ground trying to make the idle speed match the computer mapping all the way up to the point that the ECU overheats and dies.

[jackmanjls]

I remembered you said that in an early thread about ECU doesn't get feedback from ISC.

I'm going to take the ISC out and run the YDS test and see if the pintle moves in/out.

[rodbolt17]

carefull with all that.
sometimes it will spit the pintle out of the ISC,
why not simply listen for the RPM change as the request changes?

[Nautical]

TPS ??Maybe loose,

[jackmanjls]

Just for verification...am I doing a Active Test where the step motor is indexed in/out and listening for the change in rpm?

[jackmanjls]

I just connected the YDS to the F90TLR and ran the Fully opening the ISC valve test.

I expected the ISC to respond immediately the the variation in the ISC but it was sluggish. In the 3 times I ran the test in all cases the rpm did increase but never smoothly. I didn't hear the 2sec rattle after turning off.

At this point all data points to the ISC, the sluggish response via the YDS testing and the lack of a rattle when turned off.

I'm going to attempt to clean the ISC and retest. If that doesn't resolve the issue then I'll spend the $$$ to buy another.

[Fidelio420]

Verdict?

Hi Jack, did you fix the problem?? Was it the ISC valve?
Thanks

[jackmanjls]

The problem was resolved. I bought the YDS 1.33 (Yama Diag Software), installed on my laptop and ran the series of static and active tests. The YDS was instrumental in the analysis. Basically, pointed me to the problem.

In the end, I removed the old ISC valve, cleaned it and reinstalled. That seemed to work fine for the week or so before the new valve that I ordered arrived. I decided to pay the $200+ for the new valve. My logic was that I didn't want any failures in the future. As of this point in time I have not had any ISC issues.

Hope that summarizes the issue. If you need further assistance on this issue contact me via this forum.