F115 stalling, idling issue

[BigKingy]

Ok I fixed it, look like the ISC was sticking. I got a 2nd hand one. Started from scratch the sync and link and now all good. If you have to do a sync and link just forget the cheap vacuum gauge you need something really accurate. The systems with tubes is way better

[BigKingy]

Hello guys,

What kind of ISC request do you see on your F115 at idle?

Mine is sitting around 55% now.

[BigKingy]

Issue came back, it is stalling again just after going back to idle like if isc is not doing his job. that's the only issue, it idle smooth, run great. Static test and active are ok (100% request increase RPM up to 1500).

The issue is only just when going back to idle, it fluctuate between 500-600rpm and stall.
My isc request at idle is around 65-68%. If I increase to 2000RPM the ISC is only going to 71%, I've read all Rodbolt post about this issue and he said it should be 100% above 1500RPM... Why would the ECU send 71% request instead 100%?


The engine worked well for 10h after I sync the shutters and replaced the ISC by a 2nd hand one.

[BigKingy]

I had a look at the engine this morning. I checked the sync it was all within the specs so I didn't touch anything. I cleaned the ISC which was already quite dirty after 10h, the request is now around 56%. Just before the cleaning it was 65-68%. I guess the ISC was sticking?

There is still few things worrying me, maybe I'm just paranoid, what do you think?
=>The ISC is still running quite hot 190F...
=>If I increase at 2000RPM ISC request is only 64%. In other post Rodbolt said it should be 100% above 1500RPM
I made a video, do you see anything abnormal: https://youtu.be/E352ZqP13YM

[BigKingy]

Or is it only going at 100% under load?

[99yam40]

someone else will have to tell you what and when it should move and why.


but I would think it should go 100% and stay there once throttle is opened so that when you bring throttle back to idle it will have a chance to ease the RPMs down slowly to keep it from shutting down

[BigKingy]

I checked another F115 and it is doing the same, only going at 61-65% above 1500rpm from 51% at idle so I guess it is how it should work.

[rodbolt17]

that TPS voltage should be steady. use the harness diagram to see what other sensors share the 5V ref.

[rodbolt17]

and you really need to read what the ISC(IAC to the rest of the world) does and why.