Hunter......I drove the Montero for 20 minutes, and she still is idling way too high......1500 RPM. If the computer does not correct this, is there a way to lower the idle?

I did look at the old IAC, and found that the shaft that pops in/out can be rotated to make it longer or shorter. So, I reduced the lenght to match that of the new IAC, and then installed it back on the engine. Cranked her up, and she idled perfectly....about 700 rpm. Backed up fine without stalling out, but after putting in Drive and moving a few yards, suddenly the IAC failed and she stalled out. So, I put the new IAC back in, and took her for that 20 minute drive......will not idle below 1500.

 

Can you turn the shaft on the aftermarket unit to set proper initial idle that way?

 

Hunter......Nope, the aftermarket IAC is a sealed unit, and cant be opened.......el cheapo. Maybe I need to glue a sock to the end of it?

 

Hunter.....I take that back.....there are two screws on the aftermarket IAC, but I dont think they were intended to be taken apart.

 

Drove the Montero again for a good hour, and the idle is still around 1500 - 1600 RPM. Not good on the engine and tranny putting her in/out of gear at that high rpm.

What is the next step to solve this high idle issue? I hate to tamper with the original throttle body idle setting screw, but I suppose that might work.
As another idea, I might remove the IAC from my other Monty and try it out to see if it solves the high idle problem. If so, I will know that after-market IACs do not work in these Monteros.

Ideas?

 

Well, I thought I would try disassembling the new knock-off IAC and see if the shaft was adjustable like the OEM unit. This new one only had 2 phillips screws that held the unit together. After removing them, it pulled apart with no problems. I rotated the shaft, and it did actually allow the end to stick out further. So, I twisted it a few times until it was about 33mm in lenght, which increased its length by about 4mm.....from 29 to 33mm. See pic:








I tried to measure the depth of the hole which the IAC slides into, and it was about 29mm to where the inner port would begin to touch the tip of the IAC.

I thought that surely this would solve the high idle problem. Took the Monty out for a test drive, and the idle still would not drop below 1,250 (unless I came to a stop with the tranny in Drive, and it would drop to 1,000 RPM). So, this is still too high. I suppose I could try twisting the IAC all the way out and give that a try, but am doubtful that it will solve the problem.

Other suggestions???

 

Update: I removed the IAC from my other 94 Montero SR (identical model), and mounted it into the Montero I have been having this idle issue with. I had high hopes that this would solve the idle problem. I cranked her up, and at first the idle was around 1200, and then dropped back to what was normal......around 700. But then the idle started getting erratic and dropped down to around 200 RPM, close to stalling out. So, I am back at square one........same symptons the Monty had when this issue began......cranks up, but does not want to hold idle. Now I think that it is not an issue with the IAC, but something else.

Guess I will have to remove the throttle body and see if I can find some other issue. In this picture, there is another sensor on the back side of the throttle body.....I guess this is the throttle position sensor? Maybe this sensor is bad?




Sensor mounted to the left of throttle body is "throttle position sensor"?"

 

Hello StudebakerHawk,
I've read your last post and have been pondering on the possible solutions. As far as adjusting the length of the IAC control rod, I'm sure there are vehicles where that how idle speed is adjusted. However, if that were the case, you need to be able to adjust the rod protrusion length with the sensor on the vehicle with the engine running. It is kind of like the IAC on my E30 - it has an adjuster screw that you can turn in or out to get to the "happy" zone, where the computer takes over. I don't think the control valve on the Mitsubishi engine is that type. I've read up some more info on my Montero idle control and I can figure out is - it is fully computer controlled. By the looks of it, my IAC is exactly the same style as yours (mounted below throttle plate), so i would venture to guess, your '94 Montero also has full computer control of the idle speed. The more I think about it, I'm starting to wonder if your high idle speed is result of something else not working right. I can't quite put my finger on what it could be. Several possibilities:
1. Vacuum leak. Do you have an ability to pull live data feed from the computer to see what all the parameters show? Trying to see what is there, so that we don't have to grope in the dark.
2. Some plugged air passage in the throttle body. Pull TB and clean it thoroughly.
3. Incorrectly plugged vacuum hoses on the TB or the throttle body gasket installed backwards.
If you can post a photo of your vacuum lines and the tab on the throttle body gasket (where is it at?). Perhaps we can get it figured out.
Let me know if you can pull live data stream too.
Good luck.
HunterD

Hunter......Thanks much for the detailed reply. That makes sense.....that you should be able to adjust the length of the IAC rod with the engine running......so, in this case you cannot do so, and it appears that the computer will adjust the rod lenght electrically no matter what the lenght is when installed.

1. Pulling live data: I will check again, but I had thought that being a 1994, the code readers did not work on it.
2. Throttle Body.......that was my next step, to pull it off and do a thorough cleaning.
3. Gasket installed backwards......well, it had been running fine for over a year, and suddenly one morning it would not hold idle. So, gasket should be fine.
Vaccum hose.....i guess it could have become plugged......or maybe a crack developed.
4. Will post more pics of the TB.

 

StudebeckerHawk, we can eliminate the gasket on TB. I can see the tab on it in the last photo - it is installed correctly. Your vacuum hoses are routed differently than a newer on the newer model, do I can't confirm visually the all is in the rift place. Looks correct by the shape of the codes and pipes. Before pulling throttle body... Did you have a chance to check EGR valve? Engine with stuck open EGR will rum OK, but will not hold idle.

 

Hunter.......Thats a great tip.....the EGR valve. Here is a pic of the engine, and then detailed pics of the EGR:




EGR Valve:




Other side of EGR:







I checked in the Shop Manual, and it is confusing.....they showed the EGR being located way over near the brake resevoir, mounted to the battery holder.....I guess they goofed, and that was for the other engine. So, I will remove the EGR and also the throttle body to give it all a good cleaning. Could be you hit the nail on the head with this EGR postulation..........
Will get back after I have time to tear into it this week.
Thanks much for all your valued expertise on this forum.