What does the code po85 mean for a 1994 cadillac deville
It means that the throttle body is dirty and the deposits in the
throttle bores are restricting air flow at idle to the point that the
idle speed control has no more authority to maintain the correct idle
Take the air cleaner off, hold the throttle wide open and look down the
throttle bores. Spray the throttle bores with carb cleaner and scrub
the bores and backside of the throttle blades with an old toothbrush.
Cleaning the deposits off the bores and throttle blade backsides it will
restore the idle air flow to the correct level. When the throttle
body is clean, disconnect the battery negative cable for 60 seconds to
reset the idle learn offsets to the "clean throttle body" default
While you are in the throttle body and looking down the bores....see the
two tubes sticking up at you from the intake manifold floor just below
the throttle blades...??? Those are the EGR tubes and they are NOT
supposed to be full of carbon and crud. Rod them out thoroughly with a
piece of stiff wire to remove the deposits. Go all the way down thru
the tubes to the cast passage below and make sure that they are clean
and unrestricted so that the proper amount of EGR can flow.
Turning the key to the run
position extends the ISC anticipating a restart, so if the setting is
incorrect it would not erase a hard code. Just turning the key to run
would light up both the service soon and service now lights as a bulb
check, in other words, letting you know the bulbs work. Do you have the
factory service manual?
The ISC adjustment is simple on this car. With
the engine running and at operating temperature, You raise the throttle
arm slightly with your right hand and push the shaft of the ISC in to
fully retract it with your left hand. With constant pressure on the ISC
shaft it will slowly retract. The very second it bottoms, you quickly
remove the wiring connector to the ISC. Now you should have a very low
idle and a gap between the throttle arm and the tip of the ISC. Approx.
0.060 of an inch. Once you know the gap is correct, shut off the engine,
wait 10 seconds and reconnect the ISC wiring. Restart the engine and
the ISC is set to spec. The TPS setting must be verified at this time.
At minimum idle, ISC not touching the throttle arm, and unplugged, the
TPS should be reading approx .0 or .1. Once the ISC is reconnected, you
should see a TPS reading of approx. .5 at idle. with the A/C off.
code can be erased but will continue to reset as long as the reason for
it has not been corrected. Idle learn procedures were designed into
later year engines with multi port fuel injection to adjust idle
regardless of the amount of coke build up within the throttle body. Your
fuel injection system does not build up coke or deposits because the 2
injectors spray down thru the throttle body, effectively cleaning the
throttle body while running. Alot of owners adjust the ISC as if it were
a throttle stop screw on a carb. guessing as they go. The ISC and TPS
"MUST" be in sync to get the best off throttle response and smoothest
idle. Adjusting the ISC without verifying gap or TPS voltage usually
results in a surging or too high warm idle. You say the car failed at
idle. For what reason? CO or HC? or idle too high?
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Jul 20, 2010 |
1994 Cadillac DeVille