420A 2gNT IAC vs ISC ?

[turbotoad]

I've been searching the site for answers to my stalling/low idle problem with my 96' Talon ESI (non-turbo). From what I have read it sounds like I may have a problem with either the IAC/ISC, TPS, ECU, or even a CAT. But I'm a little confused on a couple of these acronyms.....

Are the IAC and ISC the same thing? Are these the same components (mounted on the TB)? I know there are two "sensors" located on the backside of the TB with one being the TPS and the other being the IAC. But I keep seeing both IAC and ISC being thrown out in different threads and I'm not sure if they are talking about the same part.

Where is the ECU located? Is this the "computer module" mounted between the battery and the engine compartment fuse-block? Or are people refering to the ECM under the radio?

 

[bosljeff]

I've been searching the site for answers to my stalling/low idle problem with my 96' Talon ESI (non-turbo). From what I have read it sounds like I may have a problem with either the IAC/ISC, TPS, ECU, or even a CAT. But I'm a little confused on a couple of these acronyms.....

Are the IAC and ISC the same thing? Are these the same components (mounted on the TB)? I know there are two "sensors" located on the backside of the TB with one being the TPS and the other being the IAC. But I keep seeing both IAC and ISC being thrown out in different threads and I'm not sure if they are talking about the same part.

Where is the ECU located? Is this the "computer module" mounted between the battery and the engine compartment fuse-block? Or are people refering to the ECM under the radio?

Yes, IAC and ISC are the same (unless I've been mislead). It is the thing that is actually part of the whole TB assembly. The TPS is on the side of your valve cover that is circular and I haven't heard of computer module, but if it is your ECU, yes, it is below and forward (towards engine) of your radio. I got to it easiest from the passenger side but you need to remove some bolts on the driver's side as well. If you get a Hayes and/or Chiltons, it will help you out some. Hope that helps.

 

[turbotoad]

Yes, IAC and ISC are the same (unless I've been mislead). It is the thing that is actually part of the whole TB assembly. The TPS is on the side of your valve cover that is circular and I haven't heard of computer module, but if it is your ECU, yes, it is below and forward (towards engine) of your radio. I got to it easiest from the passenger side but you need to remove some bolts on the driver's side as well. If you get a Hayes and/or Chiltons, it will help you out some. Hope that helps.

Huh?!? The TPS is on the side of the VALVE COVER?!?! Ummmm, that doesn't sound right. Shouldn't it be ON the TB itself?

I'm pretty sure the TPS is located ON the TB just above the IAC. The question I had was if IAC and ISC are different names for the same part? There is another electrical connector directly under the TB opening and I'm not sure what it is.

 

[steve]

Since he has a 2G NA things are a little different because of the chrysler 420a engine in that car.

The ECU/PCM/WhateverMOPARcallsit is the box by the battery. DSM's with mitsubishi engines have the ECU in the center console.

Don't know enough about 420a to say for sure where the ISC/IAC/WhateverMOPARcallsit is located on the TB but basicly the name just depends on which manual you learned it from. The parts are different between the 420a, the 1G 1.8L , and the 4G63's but they do the same thing.

Steve

 

[bosljeff]

Here:

 

[turbotoad]

Yea, mines the 420A. Looks nothing like those pics.

 

[bosljeff]

ISC out (from crebotech.com)

 

[bosljeff]

Yea, mines the 420A. Looks nothing like those pics.

Oh, sorry.

 

[steve]

BTW bosljeff, the thing circled in red in the first picture is the CAS not the TPS. The CAS provides cam and indirectly crank angle positioning information where the TPS provides throttle opening information.

Steve

 

[RoasT BeeF]

Yeah dude the TPS is the little black thing on the front side of the TB right about where the corner of the white box is. That thing you circled is just a valve cover breather.

And from what I know about 4G63's there is no IAC (idle air control) its called an ISC (idle speed control). Dont know if the same can be said about the 420a motors but it HAS one or the other. Some people get mislead and think they are the same thing. They are not.

 

[bosljeff]

BTW bosljeff, the thing circled in red in the first picture is the CAS not the TPS. The CAS provides cam and indirectly crank angle positioning information where the TPS provides throttle opening information.

Steve

Hell, thanks. I forgot. I just remember when I tapped my shift lite I tapped into a wire coming out of that. It was a long night, I don't remember much from it. Damn all these acronyms. Thanks for keeping me in check.

 

[Engineblow1]

The TPS sensor is located on the right side of the throttle body toward the back. The 420a has a IAC valve that is located directly below the TPS sensor. The IAC can be a bit of a pain to get off. The easiest way is to remove the throttle from the throttle body. The IAC and TPS comes off with it.

 

[turbotoad]

OK, thanks for the responses!

So the 420A has just the IAC and the ECU is mounted just in front of the left shock tower? Now I just need to start testing the sensors and figure out if the ECU is starting to go!

The car was acting up again tonight. It started up but the idle immedietly dropped to about 200RPM and bounced around a little before leveling out at about 800RPM in park. Once in gear it varies between 500-600RPM and then briefly hunts between 300-500RPM just after coming to a stop. It also stalled a few times after stopping at stoplights.

BTW, After I turn the car off there is a very high pitched whistle (almost dog whistle pitch)sound coming from the ECU (mentioned above). It's not real loud but can be heard from a few feet away and lasts for about 1-2 minutes after the car is turned off. Could this be a sign that the ECU is self destructing?

Thanks again for the input.

 

[turbotoad]

"BTW, After I turn the car off there is a very high pitched whistle (almost dog whistle pitch)sound coming from the ECU."


Any sugestions as to what this could be?

Bump

 

[turbotoad]

UPDATE;

Well, I attempted to do some testing with a multimeter and a vacuume gauge. Everything seemed to be ok except that the Chilton book I was using as a guide had no information about testing the IAC/IAS. Apparently the only way to truely test it is with a very exspensive scan tool.

So I finally gave in and took the car to see Satan (dealer).

Yep, the IAC was bad and Satan gladly bent me over to the tune of $299.00 in order to fix it. OUCH!!!

I figured that replacing the IAC required removing the TB and a bunch of other work. So I passed on buying a new IAC from the local parts man for $110.00 and installing it myself. But after getting the car back from Satan and looking at the old parts it was apparent that I could have easily installed it myself. Thus saving $189.00!!! Damn it all!!! Oh well, live and learn.

 

[RoasT BeeF]

You win some, you loose most.

At least its fixed now.

 

[2g-gst]

A new IAC fixed the abnormal idle just like that? Reason I ask is because I just put a 1g TB onto my 2g and I have a check engine light on as well as a wierd idle every once and awhile. Just trying to troubleshoot this. thanks!!!

UPDATE;

Well, I attempted to do some testing with a multimeter and a vacuume gauge. Everything seemed to be ok except that the Chilton book I was using as a guide had no information about testing the IAC/IAS. Apparently the only way to truely test it is with a very expensive scan tool.

So I finally gave in and took the car to see Satan (dealer).

Yep, the IAC was bad and Satan gladly bent me over to the tune of $299.00 in order to fix it. OUCH!!!

I figured that replacing the IAC required removing the TB and a bunch of other work. So I passed on buying a new IAC from the local parts man for $110.00 and installing it myself. But after getting the car back from Satan and looking at the old parts it was apparent that I could have easily installed it myself. Thus saving $189.00!!! Damn it all!!! Oh well, live and learn.