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what are input signals to computer to cause the idle air control(IAC) the plunger to retract with ignition key on and engine not running.
My problem :IACMotor is locked with opposing voltage in motor coils or solinoids.Key diagnostic indicates a MAP voltage problem.
No difficulty with normal running except for irregular cold start.
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Hello George,
There are many inputs that determine the position of the idle air bypass opening: throttle position sensor, speed sensor, coolant temp sensor, neutral safety and brake switch position. It operates with two separate coils, one to open and one to close the air opening. I am not sure how the voltage is applied to the two coils, perhaps one at a time, perhaps in opposition with different voltage values?
In any case, I think if you aren't getting a code for it then it is o.k. and it would seem to be "locked" unless something from the sensors was telling the controller to change its position.
I would take the MAP voltage problem as real. In most likelihood the reasons for a code are: seal between the MAP and the intake manifold may be leaking (tighten screws), the electical plug may not be making good contacts (open and clean) or the wires might be damaged (so look those over) or the MAP itself has stopped working which can be the reason for a MAP voltage code. If you have a voltmeter try probing the signal wire red/dark green with a fine needle: with the ignition on and the engine at rest it should read about 4.5 volts between it and the engine block (ground). If you start the engine it should drop to 1.0 -1.5V or so and if you raise the rpm it should raise the voltage to 4.0V or so with the throttle full open. So check that out and let me know what you find.
Roland ---follow-up
The MAP CHECKS OUT as to voltage change with RPM.My IAC has a constant voltage on opposing coils.You set it manually and it remains in that position with the key on/off engine not running.Computer -?-
Answer -
Hi George,
I just discovered why perhaps I didn't hear from you today or yesterday: the Allexpert website had me showing "maxed out" though I had only answered 3 questions yesterday and none today, whereas I was signed up to answer 5 a day. Something is wrong with their system evidentally.
If you were disappointed, please forgive them their error.
I should be 'good' for the rest of the day, if you have a further question about your car or want the copies.
Roland
Hi George,
I am not certain that you can determine that the IAC is frozen in one position without the use of a scan tool such as the Chrysler DRB II. I have the Haynes manual and it has a nice write up on the IAC and how to evaluate it. Rather than my typing all that in may I xerox copy and snail mail it to you? Just give me a postal mailing address and I'll put in the mail on Monday. Because except for the cold starting irregularity I would not do anything drastic yet like getting a new controller. Instead go over the write-up from the Haynes and then decide. I'll also send you the write up on the MAP sensor. You might try disconnecting the battery for 5 minutes to erase the stored MAP code, then see if it returns again.
Roland
HI ROLAND
MY ADDRESS IS : GEO. CURRIE
12605 CEDARBROOK LA.
LAUREL MD. 20708
THANNKS FOR THE EXTRA HELP.
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Hi George,
I'll get those pages into the mail for you.
You probably found that I wasn't accessible for a week. It was the allexperts site itself was at fault and we couldn't get them to respond.
Roland
HI ROLAND ,
RECEIVED YOUR PAPERS IN THE MAIL.THE INFORMATION DOES NOT GO FAR ENOUGH FOR MY DILEMMA.THANKS AGAIN FOR YOUR HELP.I STILL NEED THE LOGIC FOR DRIVING IAC MOTOR TO RETRACT WHEN THE IGNITION IS ON AND THE ENGINE IS NOT RUNNING.
GEO.
AnswerHi George,
An AC Delco training manual I have shows the driver circuit for the IAC in the OBD-I system. It shows there to be a single driver for each of the 4 leads of the IAC unit (the ends of the two opposing coils) and it states that the drivers can either put out 12V or ground as ordered by the controller (which uses coolant temp sensor, distance sensor, throttle position sensor, and various switch inputs operations) The Snap-on manual (eighth edition, 11/97) says that the IAC motor cannot be activated by the controller with the engine not running because it's logic requires there to be an rpm signal present or it won't put out a signal.
That is all I know. I hope that helps.
