F225 Runs better w/idle air control disconnected

[morayinc]

Hi all, I have a F225 02. The idle has been rough since my last post. The beast ran fine going out, then when I idled down to reel in the fish, it konked out. I got it started, it ran at *****ing speed throttled down and it failed to idle again. Must throttle up in neutral to start, then gear-n-go. While trouble shooting, I did find an interesting thing out. While it idles rough, I can disconnect the idle air control the idle smooths right out. I do not hear the “chatter” as others have recited. Recap old issues: I found the LP relay was bad it was replaced worked fine. The LP pump is lifting fuel, the HP pump sending 42lbs press. The VST cleaned, new plugs and replaced, all filters. Morayinc

[rodbolt17]

then you need to test the ISC.
can be done with the laptop.
can be done both statically and dynamicly.
be aware a stuck ISC can burn out the ECU and ign coils.
there are NO codes associated with the ISC.

[morayinc]

no trust in mech

I took to the mech and gave them a written list of what I wanted checked. I had the diagnostic look at the engine. They found it to be out of time by 15 degs, very odd. The test revealed a need to replace the shift sensor due to a trouble code. I guess the feedback from the IAC is not checked by the computer. They indicated IAC was okay.

I think not, as it does not chatter with power applied and gets HOT to the touch. I ordered a tamper proof torx kit and a new IAC. I checked the TCS voltage and adjusted to .70v, (was too high). I finally had time to pull IAC and close off the small intake to observe the idle change. It showed a positive response. After ordering an new IAC, I needed something to do, I sacrificed the old IAC. The result is, the bearing was seized with noticeable rust on the axle/magnet. I am waiting on the new part to arrive. morayinc.

[morayinc]

I have been having so much fun I forgot to follow-up with the thread. The IAC was the problem. Works great! Morayinc.

[salbrent]

I replaced the ICS motor and it is warm to hot to the touch.
Does the ICS normally run hot?

[rodbolt17]

the ISC is normally warm NOT hot.
hot means its sticking.
sticking means it will over current the ECU.
then the ECU,ISC and ign coils bite the dust.
never pretty.
motor simply CANNOT be out of time UNLESS something mechanical failed.
simply CANNOT happen.
any one wish to argue that point?
temp gun he ISC,anything over about 200*F means something bad is about to occur.
there are simply NO codes associated with the ISC system.
the ecu commands a position and assumes it happens.

[salbrent]

thanks I will check it with a IR thermometer

[fb5558fb]

isc hot with engine off

my isc clatters when power is applied and engine runs properly. when the engine is off and battery switch on the isc is gets hot .. When the yds computer is connected it thinks the engine is running when its not. any ideas?

[rodbolt17]

fb
lets keep this on your original post.
sometimes thread hopping leads to kornfuzeshuns.