Well, you DEFINITIVELY confirmed that your original IAC has gone off to pasture. Having one coil out would completely disrupt the duty cycle and prevent proper functioning. 40 Ohms reading on all coils on new unit is totally fine. The difference is likely co.es from minute changes in coil wire size and possibly number if windings in the coil. That is not important, since the unit works by simply providing 5 v to the middle pin and then computer controlling grounding of the other pins. Did you check if you are getting 5 v on pins 2 and 5 on the farm as side?
I'm sure there is a way to test to see if your pins 1, 3, 4 and 6 do properly ground when engine runs, but I doubt you have the tools for that in the DIY toolkit.
Any progress on solving your computer communication issues? I think the two issues you're experiencing might be related. What if you get under the dash and just wiggle/connect/disconnect main wire harness on the PCM. Can't hurt to check that.

 

Hunter......Yep, the IAC "kicked tha bucket". The shop manual is calling for about 30 ohms on the IAC, but as you say, different makers probably have upped theirs to 40 and it still works fine.

I just did the voltage test going to Pins 2 and 5........both are getting a bit over 12 volts. I then checked my other 94 Monty, and it is also getting 12 volts to Pins 2 and 5 of the IAC. So, Im guessing that 12 volts was used for the 1994 model, and maybe this is a hint that it is an OBD 1, not an OBD 2 set up?

When I just checked the Shop Manual, it states that you should use "about 6 volts" to test the IAC.......so, this throws more confusion into this matter. I cant find anyplace a spec. listing the input voltage for the IAC.

As Homer often says, "DOHHHHHHHHHH!"..........

 

Hunter......Also, today I drove the 94 Monty to fetch some supplies. She started right up, but did idle too high (around 1250). After driving and warming up, it did idle down to the normal area (2nd hash mark which is about 650 I think). It seemed to be idling good at stop lights (I put in neutral), and the RPMs hovered right around 650. However, the needle did move a smidgen above or below that 650 mark, which I dont recall it ever doing in the past......seemed that she used to idle perfectly at exactly one spot and did not meander a bit up/down. But other than that slight idle variance, and the high idle at start-up, she drove fine.

I would think that if the 12 volts going to the IAC was too much, that the IAC I just put in would be burning out.....but it is not failing.

Still plan to do as you say......get to the ECM and inspect those wires.

 

12v might be normal voltage on IAC feed. I called out for 5v because I was thinking about other sensors (MAF, MAP, etc.). Those sensors also go to ground tjrough PCM and they work on 5v. There is nothing that prevents computer from having and managing several different voltage levels. If you are getting battery voltage on pins 2 and 5, you're good. I think normal idle is between 650 and 800 rpm. So, it sounds like you are in the right range. I wouldn't worry about slight variation in rpms, that is not an issue. Higher idle speed on startup is also normal. Lets hope you've finally beaten it into submission 😉

 

But it is confusing when the "92-94 Mits. Montero Service Manual" does specify that you should use about 6 volts for testing the IAC. Maybe they goofed in the manual, or they are just playing it safe so the mechanic doesnt accidently burn out the IAC with a super charged 12 volt battery. I guess 6 volts will be sufficient to see the IAC move in/out, so why apply the full load.....maybe thats their thinking. And also, it will keep the technician thinking "only use 5-6 volts on any of the sensors for testing". Not sure.......but like you said, I am darn close in having her run like she did before this incident.

Im gonna go ahead and order a plain jane code reader that reads both "OBD 1 and OBD 2".....and hope that it will read my 94 Montero codes. Maybe something will show up that will shed light on the situation.

Hey......do you have any better sources for OEM new/used parts? I would like to get an OEM IAC to put back in the other Monty, and so far the only price I have found was around $325 for the IAC (opposed to $18 for the knock-off ones). I would have no problem with a used one, as it will probably last for years.

 

Your 94 uses the same IAC as the montero sport up to 2004, with that in mind you have a lot of options to choose from. As long as it has the Mitsubishi stamp on it, it's going to be factory OEM. Could try a junk yard, or you could try the brand from Oreilly auto parts Part# AC249. I had one in my rig and it worked great for the 3 months I was using it, I only returned it because I happened to get my hands on a lower mileage OEM one and needed the money more than a spare IAC. Rockauto has it listed for $130 but it's easier to return to a local store if you need to. Junk yard is cheaper though.

 

Naeos......By George you are right.....the ORielley AC249 is a solid plastic IAC (not half metal anymore), but it does have the Mitsu. stamp on it......and its $155.

Yep, Rock Auto has the same one for $127, and with the Mitsu stamp on it. It is listed as a SNP Intermotor part, but has the Mitsu stamp on it in the picture.

 

My usual "go to" for 100% OEM Mitsubishi parts does not have IAC for your Montero. Price for it is listed at $250, but availability is 0. They do show Hundai/Kia part No: 3510333000 and 3510333010 as a substitute, but the price is still near $200.

 

When I worked at a parts store I got curious and looked up the parts interchange on our IAC and apparently (according to the parts catalog) the Kia Sorento uses our IAC up until 2004 If I recall correctly.

 

Hunter/Naeos.....200-250 still pricey for an IAC. I guess the 127 one from Rock (with the Mitsu. stamp on it) is the same thing. Or some knock off maker is illegally using the Mitsu. stamp on their cheap parts. Hard to know these days.