IAC questions

[StG58]

I have some questions about the IAC on a '99TJ four bangers.

Does the IAC fail open or closed. i.e. It seems that it would be normally closed, and the PCM would open it as required to modulate the idle speed. That would impy that if you unplugged the IAC it would be closed.

 

[StG58]

Went out and played with the IAC for awhile. Everything inside was very clean for 100,000 mile on the clock.

Interesting thing is I can cover the air inlet for the IAC with my fingers and modulate the RPMs. Nice. Can't drive around with fingers over the IAC air inlet, but interesting to know. Seems to point out that there aren't any vacuum leaks in the intake system. NAPA had an ECHLIN IAC on the shelf, so I spent $80 on replacing the one that was in there. Guess what, the idle is now 2,100 RPM vs. 1,400 RPM. The IAC that was in there might have been messed up before, but it is now. Played with it to see if there was any adjustment. Nope. But I did get the old IAC screwed up enough that the idle dropped enough to kill the engine and keep it from idling. Still runs fine off idle.

 

[Chris]

Okay, so the real question is what's the status on the PCM? Have you found one yet?

It doesn't seem like it's the IAC valve.

 

[StG58]

Yup, blew $80 on an IAC to no result Chris. Found a company down in Florida with a good reputation that will rebuild mine for $450 or so and a lifetime warranty. They also program in VIN and mileage. They were recommended by the Jeep dealership that we bought the JK from.

 

[Chris]

Yup, blew $80 on an IAC to no result Chris. Found a company down in Florida with a good reputation that will rebuild mine for $450 or so and a lifetime warranty. They also program in VIN and mileage. They were recommended by the Jeep dealership that we bought the JK from.

Just return it, they shouldn't complain as long as it doesn't look used. I've done that plenty times!

 

[StG58]

The one that was in there is probably trashed now. I'm one of those guys that can't help but monkey with a broken part to see why it's broken.

 

[Chris]

The one that was in there is probably trashed now. I'm one of those guys that can't help but monkey with a broken part to see why it's broken.

Oh, haha... okay, well at least you won't have to worry about your IAC going bad for a while (hopefully). I know that sometimes those off-brands have iffy reliability, but you never know.

 

[StG58]

ECHLIN? It's not MOPAR, but it's a good brand. They make a lot of parts for the OEMs. Been buying those parts from NAPA forever with no issues, but then again, I ran Fram filters forever as well until NAPA rebranded WIX filters. We'll see. There was one IAC locally, up at NW Chrysler Jeep in Beaverton. They wanted $169 for it. $80 was a safer bet for just giving it a try.

 

[Chris]

$80 is a safer bet for sure. I doubt it will fail anyways, usually that's something like the off-brand of CPS sensors or O2 sensors.

 

[StG58]

I have a pretty good relationship with the local NAPA guys. One of them is a Jeep guy, drives and off roads Comanches. The girl at the front counter drive a TJ (her mom's) and they have a few crusty old farts behind the counter that grumble about TJ's not being real Jeeps. One drives a pristine CJ5, bone stock and absolutely beautiful. They are pretty free with opinions and advice. Plus I get a discount.

 

[Chris]

Haha... They grumble about TJs not being real Jeeps, we grumble about JKs not being real Jeeps... Funny how that works!

But we can all agree that anything other than a Wrangler (with the exception of a Cherokee, Comanche, Wagoneer, and any of the old stuff) is not a real Jeep.

I'm referring to things like the Jeep Renegade, the new Cherokee, Grand Cherokee, etc. They're just Fiats with a Jeep badge

 

[EJD]

What size torx to remove the IAC and housing? Think I may clean mine tomorrow.

 

[StG58]

What size torx to remove the IAC and housing? Think I may clean mine tomorrow.

T-20. I used a torx bit from a bit set with interchangable bits and put it in a 1/4" socket on a 1/4" short handle ratchet. It's faster and easier to remove the housing and then remove the valve. The air intake ducting does need to come off to get into everything.

 

[EJD]

T-20. I used a torx bit from a bit set with interchangable bits and put it in a 1/4" socket on a 1/4" short handle ratchet. It's faster and easier to remove the housing and then remove the valve. The air intake ducting does need to come off to get into everything.

I'm curious to see how gunked up mine is with over 150k on it and i'm sure it has never been cleaned before. Also curious to see if just cleaning it makes any noticeable differences.

 

[EJD]

The air intake ducting does need to come off to get into everything.

Your are referring to the 4 "10mm bolts" correct? or just the hose?

 

[StG58]

Your are referring to the 4 "10mm bolts" correct? or just the hose?

Just the air box and the hose. You can probably unplug the electrical connector on the IAC and pull the IAC itself without removing the air box and the air duct, but I just pulled mine. It's a lot easier to see what's going on and to maneuver the tools around in there. The only problem I had was the lower rear bolt holding the IAC assembly on. My hands are rather large (no Trump jokes, OK?) and not as nimble as they used to be, so I had to take extra care not to drop that bolt into the Black Hole of Calcutta taking it out and putting it in. The torque specs on those bolts are really low, something like 8 - 10 inch pounds, so just snug them up.

My IAC was really clean after 100,000 miles.

 

[EJD]

Just the air box and the hose. You can probably unplug the electrical connector on the IAC and pull the IAC itself without removing the air box and the air duct, but I just pulled mine. It's a lot easier to see what's going on and to maneuver the tools around in there. The only problem I had was the lower rear bolt holding the IAC assembly on. My hands are rather large (no Trump jokes, OK?) and not as nimble as they used to be, so I had to take extra care not to drop that bolt into the Black Hole of Calcutta taking it out and putting it in. The torque specs on those bolts are really low, something like 8 - 10 inch pounds, so just snug them up.

My IAC was really clean after 100,000 miles.

Ok cool and thanks, I just watched a YouTube video where a dude unbolted the 4 (10mm bolts) for the whole assembly and took the IAC off and the housing then, sprayed everything and cleaned it all then just bolted everything back together. I'm new to these sorts of tasks so I always like to ask if its something I should not take apart. But it looks like a tight squeeze trying to unbolt the lower housing bolts without removing the whole assembly. I might just clean everything.

 

[StG58]

It's actually not to bad to get the IAC housing off once the air box is off. Using a short handled 1/4" drive wratchet made a world of difference though. There's enough room to manuver that in there, but no way to get a normal torx driver in there.