1994 3.0L Ford Taurus RP Ms. change.

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  #1  
Old 10-23-12, 03:17 PM
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1994 3.0L Ford Taurus RP Ms. change.

I have a simple 1994 3.0L Ford Taurus GL. When I pull out of my driveway and put the shifter in drive, the idle is fine for about 1/2 block and the idle just lowers and the transmission downshifts for no apparent reason. Then, I let off of the gas due to the trans. downshifting, give it more gas, and it speeds back up and changes back into drive. Well, about another 1/2 block, the ugly demon under the hood has to remind me "who is in charge under here" and repeats the whole process over again. I've had enough, time to park it and try as I might to fix it. The Check Engine Light method of reading codes is all I have access to. My local Auto Zone does not have nor use the K.O.E.R. Scanner anymore. They are mentioning that I might have a bad Idle Air Control Sensor. They did caution me that the sensor may not be the problem. I don't think that I could drive it 2 miles to the shop. What do you folks think about my tired Taurus?
 
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  #2  
Old 10-23-12, 03:30 PM
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I'm a little surprised it's still on the road; that's mostly because you have the 3.0 and not a 3.8 which were notorious head gasket blowers.

Unless you are driving down the road with your foot off the gas, the IAC would not be a factor. Once the throttle comes off the idle position (closed) the IAC is out of the picture. More likely would be a throttle position sensor, which tells the computer (and subsequently the transmission via the computer) how much "go" you want. You really need to start with a code read to try to find a starting point.

BTW, the other early causes of death on that vintage Taurus/Sable was the tranny which was known to go south with as few as 30,000 miles on the ticker.
 
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Old 10-23-12, 06:01 PM
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TG, can you explain this better?

Once the throttle comes off the idle position (closed) the IAC is out of the picture.


As I remember well my Taurus ISCU, which was a basic solenoid with push rod ALWAYS touching pintle valve lever. I do not remember if it could have been manually rigged with a screw. Basically, what it was doing, it was monitoring idle speed below "pedal released" level by pressing on lever.
It sorta sounds like as if when his idle drops, ECU "thinks" he lets go off gas pedal and downshifts.
 
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Old 10-24-12, 04:56 AM
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If you were to be able to rig up an on-off switch to the IAC, once you are cruising down the road you could turn the IAC off (although this is theoretical; switching it "off" could affect the computer in an unrelated way). The IAC on my wife's Camry has been essentially dead for several years ($250 to replace! ), so it idles a bit below optimum, but has no effect on driveability. The IAC is simply a valve that allows a small amount of computer-regulated/moderated air to bypass the "closed" throttle plate. Once the throttle plate comes off idle the small amount of air going through the IAC is overshadowed by the volume going past the throttle plate. I don't know that the IAC has any inputs to the computer beyond idle speed; I don't think there's any relationship that would cause a downshift as would a TPS. And then vehicle speed comes into play, too (VSS) because the tranny would never (you would hope) downshift when you're doing 70 mph down the Interstate. But of course this is a Ford, so you never know.
 
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Old 10-24-12, 07:42 PM
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oh, no, no, what my Ford had - and bet, his too - was a simple solenoid, controlled by ECU. rod comes out, pushes on pintle valve lever, RPMs go up. rod retracts, RPMs go down.
that's why it sort of makes sense to think of THAT type of idle control device causing trannie havoc.
 
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Old 10-24-12, 08:08 PM
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i would go with the-tow-guy. first check your trans fluid level (running in park) they always leak.
 
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Old 10-24-12, 08:16 PM
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Good point on the fluid.

That solenoid is more what I would call a throttle-up solenoid than an IAC. The IAC, by definition - idle air control - moderates idle air to achieve the proper required idle speed. Those Fords only had that solenoid and not a true IAC? Didn't know that or have forgotten it.
 
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Old 10-25-12, 07:41 PM
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found it.
Ford Taurus Standard Ignition Idle Speed Control Motor SA3 at Auto Parts Network

damn, when I had mine replaced, after it did "toyota" stunt on fwy, it was only $75 back in time. But you can see how thing works. It's either solenoid, or stepper motor with push rod.
 
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Old 10-26-12, 04:24 AM
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Now you know why I haven't replaced the IAC on wifey's Camry.

I'm guessing that's 90's technology on idle control; I don't think anything uses a mechanical control now. Anybody know?
 
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Old 10-27-12, 07:33 AM
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now you also know why I have learned a lot off that 87 Taurus
 
  #11  
Old 12-09-12, 09:36 AM
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First, I would like to thank everyone for their input to my IAC problem. Second, I replaced my TPS and my car runs worse than ever. I do read codes 33, 122, 1211 and 211 using the MIL.The idle in park is ok, but I'm still in the driveway. I push the accelerator and the engine starts to missfire and almost wants to shut off. My Chilton manual says that the TPS is not adjustable. I want to buy a digital multimeter and measure the DC volts coming to the TPS and how the voltage increases when I accelerate. I found this info. on youtube. No direct specific videos for my 94 taurus though. Am I barking up the right tree? Should I clear my KAM before I try to adjust my positioning of the TPS.
 

Last edited by jae94taurus; 12-09-12 at 09:55 AM. Reason: Forgot to list fault codes.
  #12  
Old 12-09-12, 09:54 AM
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why don't you take her to any local shop and do computerized diagnostic? will cost you $60-70, but will take guesswork off your shoulders. Learn what is wrong with it and DIY replace the part. your car is apparently sick, get doctor involved.
 
  #13  
Old 12-16-12, 01:46 PM
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Thank you for your advise. I hope that I can drive it 2.5 milles w/o the first stage catalytic converter heating up again. I really do need to see my local garage. Then as you mentioned, hopefully, I can do the repair (s) myself. I have put the check-up off because of finances. So now I have to bite the bullet and JUST DO IT!
 
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