On my 92 Grand Caravan 3.3 I have a high idle problem that
consistently trips the Code 25 (IAC circuitry). Idle at startup is
around 1500 RPM's and moves steadily higher(1850+) as engine warms.
Here is what I have checked and replaced.
Idle Air Control Motor
Cleaned throttle body and plate and replaced gasket.
Swapped out Engine Control Module(ECM) from another Caravan(exact
No known vacuum leaks or other gasket leaks
No other codes found
The code 25 immediately sets itself even after I disconnect the battery
for an extended period. I even disconnected the ECM and reconnected.
It will show the code before I ever start the vehicle again. It sets
itself when key is in on position and checks signal voltage. I am
suspecting wiring. Resistance tests appear normal. I would like to get
this car past 300,000 (only 57 miles to go).
It starts great and ran very well before this high idle issue. For
those who know a ton more than me: What would be your next steps if you
were in my shoes? Thanks
The most likely culprite here is the EGR valve staying open during idle
which it should not do under any circumstances. Disconnect the vacume
hose from the EGR and start the engine. using a small hammer lightly
tap on the EGR valve if it is stuck it will most likely loosen itself
ck to see that you do not have vacume at the EGR hose at this time as
well. If the idle does not come down use a small mirror and flashlight
to verify that the diaphram on the EGR is in the down position (away
from the vacume port) if it is then the EGR is closed.
ck the IAC harness connections at both ends and ck the IAC wires for
continuity while pulling on the wire harness..
There may be carbon build up in the idle channel in the throttle body
generally these vehicles start burning oil at the 100k mark and this
fouls op the works.
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