How to replace an IAC motor on a Gen 1

maverickagm

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The Idle Air Control (IAC) motor is on the back of the intake on the passenger side. You may be wondering if you can actually get it off without removing the intake. Yes you can. Here's how.

Tools:
7/16 regular wrench.
7/16 stubby wrench. It's in a tight spot and a regular wrench will hit a bunch of pipes.
7/16 socket on a socket wrench with a slimmer head.
10mm socket
needle nose pliers
philips screw driver
T20 socket or screw driver

1) Engine should be cool to the touch. Open the hood and both doors. We're going to make some working space. Remove the four screws for the wiper cowl. Two of the screws are accessible when the doors are open. You do not need to remove the windshield wipers or hoses. This will create some space so you can fit you hand between the IAC and the wiper cowl. With the screws out, the wiper cowl will lift a bit. On the passanger side, one of the screws goes into a bracket. This little bracket can get in the way but can easily be removed with a 10mm socket, as seen in this photo:

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2) Unplug the IAC electrical connector. From the driver's side, you can extend your hand under the wiper blade cowl to reach the connector. It should be pretty easy.

3) Using needle nose pliers, remove the horrible clip that holds the air intake hose to the IAC housing (the top one). Try not to rage-quit here. It's a bit tricky, but not too bad. The next 2 photos show both hose ends removed, but removing only the top one provides enough working space

4) We're removing the IAC motor and housing together. Remove the top bolt. I found a 7/16 socket wrench to be easiest for the top bolt.

5) The bottom bolt is the harder one. Use the 12 point side of the stubby 7/16 wrench, not the open ended side. Use your right hand to slide your hand over top the IAC and under the wiper cowl. Use your middle finger to locate the bolt. Use your left hand to hold the wrench. You then use your right-hand middle finger to go through the 12 point side of the wrench and to slide the wrench over the bolt head. Now you can loosen the bolt 1/12 turn at a time. Eventually you can get a bare socket around it or just your fingers to remove it the rest of the way. There is a gasket for the IAC. Don't loose it. I found myself alternating between the regular size wrench and the stubby wrench. Here is 2 pictures of a regular sized 7/16 wrench on the lower bolt. As you can see, space it tight, but it can be done. In the second photo with my hand, the right-hand middle finger is on the bolt head. This way I can remove the wrench from the bolt head, rotate the wrench, then easily relocate it onto the bolt head. I'm only turning the bolt head about 30 degrees at a time. This is why using the 12 point end of a stubby wrench is critical. There's no room for a socket wrench, u-joint, or crows foot.
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6) Now that the IAC is out, remove the motor from the housing using the T20. Now install the new IAC motor onto the housing. The pintle will likely be at a different position than the one you removed. This is fine. I found my car idled at 2000 rpm then slowly came down as the PCM closed the pintle. There is no spring on this type of IAC pintle. My understanding is that there's 4 wires. 2 wires for moving the pintle in one direction, and 2 wires for the other direction.
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7) Critical step. When reinstalling the IAC, it's going to be easy to get your 12 point wrench around the bolt head. As the bolt tightens, it will get very hard, or in my case impossible. What was happening is the T20 screw from the IAC motor would hit the wrench and prevent it from fitting around the bolt head. Trim this screw with a dremel cut off wheel. That will make the difference of spending hours, or mere minutes, when trying to tighten the 7/16 lower IAC bolt. From this photo you can see I only trimmed the lower screw since I used a socket for the top 7/16 bolt, and a socket is slimmer. The top screw still protrudes the IAC housing.

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8) To install, reverse the order.

All in all, this isn't too bad of a job. Just make sure you have the right tools and you trim that screw on the IAC motor. Smaller hands will benefit here.
 
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99RT10GTS

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Very nice write up!! The instructions will apply to all cars 1992-mid94. The changed intakes and location of the IAC was moved to the front of the intake, passenger side for better accessibility
 
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maverickagm

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You can see my thread here on what I'm trying to solve:


However in my case, I was wrong to change this part. My existing part was fine.

Generally speaking, symptoms of a bad IAC motor would be an idle that's too high or too low. The PCM would be trying to adjust the air/fuel ratio, or idle speed, by telling the IAC motor to open or close. But it could get stuck, or the motor (which is really just an electric stepper motor that moves a pintle forward and back) could be electrically damaged.
 

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