I have an 89 full size, 5.8, Eddie Bauer. The motor was rebuilt about
50K miles ago, the transfer case was replaced this month and the
transmission was serviced at the same time. The truck also has a new
fuel filter, and the emissions were all gutted and rebuilt in the last
The problem is with the low idle, if the truck kicks down from fast to
slow idle, it stalls about 50% of the time. This seems to have started
after the transmission service and new transfer case.
Would resetting the computer restore the idle to default? If so, how
do I do it? If the computer won't do the trick, is there an easy way
to up the idle speed on an EFI engine? Is there a chance that a vac
hose is unplugged someplace that is causing the stalls?
On 11 Oct 2006 10:05:26 -0700, email@example.com wrote:
The ECM can be reset by disconnecting the battery for 10
minutes or so. Before you do that, make sure all the vacuum
hoses and wiring connections are proper and not leaking.
Make sure the throttle body is clean. There are solvents to
do this. You may want to make sure you spray some of the
solvent into the IAC bypass holes inside the throttle body
to claen up the IAC a bit. If that doesn't do it, remove
the IAC and soak the valve end in a good solvent to clean
it. If it is really bad, it may have to be replaced. If
you disconnect the battery to reset the ECM, start the
engine without touching a thing and let it idle for 5-10
minutes. Without touching the throttle, move the
transmission selection into each position for a few seconds
allowing the ECM time to stabilize the idle speed and
relearn it's idle parameters. After that, drive the vehicle
normally for a few miles around town to allow the ECM to
relearn to operating paramaters. It should be good to go
after that. If the stalling continues after cleaning the
IAC, you may have to replace it. The IAC can get gummy
enough not to work correctly without setting a fault code as
it would in the event of an electrical related problem. If
anyone has screwed with the base idle setting, you may have
to get a manual and reset that by the book. If the base
idle is not correct, the IAC cannot control the engine idle
as it should. The base idle speed is set below the normal
idle speed controlled by the ECM via the IAC. If it is not
correct, the ECM may start to do funny things with fuel
control. The correct idle speed for your engine is
determined only by the ECM.
All of that said, it is possible that the transmission is
not fully releasing the torque converter at idle as it
should. This is rare but possible with the AOD trans if the
OD band is setup a bit too tight. That can be checked by
removing the pan and valve body. If you notice a hard thunk
on engagement, that "may" be related.
Thank you!! Great post, I'll head out to Walmart tonight and get some
cleanser for the IAC and see if I can get that thing cleaned up. I
really appreciate the help, this is great advice!
It is attached to the Throttle body by two bolts, where it routes air
around the throttle plate Find where your accel/Cruise Control
linkage attaches.. that's the throttle body, disconnect the air tube to TB.
You'll see one port in front of the throttle plate.
Clean the area around throttle plate, as well.
Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!
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