I think my ISC is dying <img src="/forums/images/graemlins/frown.gif" alt="" />

Symtoms;
Cold start idle ~ 1200
Slowly drops to ~ 750

After driving for about 20 mins the engine will NOT idle, if left it stalls out. A real PITA for an auto.

I have removed & cleaned the ISC, just used gas & a cotton rag, but this has made no difference. I think the ISC is breaking down under heat-soak from the engine, as it seams fine for a while.

Anyone have any other thoughts ?
There's one on ebay ISC HERE

SteveN

I know some on here have disconnected their IACs, and set the base idle using the screw on top of the throttle body. You might try this as a diagnostic to see if the lack of idle at normal operating temperature goes away. If it does, certainly your IAC is most likely the culprit.

I recently replaced mine with a new IAC from dsmisc.com... I don't know how price/shipping to UK compares to your EBay find though.

Best of luck to you!

Eric W.

It's easy to check it if you have a meter. Need to pull it, but you've already done that. Need the FSM to check the readings range. There are three pairs of pins that orient to the three ring-things inside. You need to meter them. A bad ISC will throw a value out of range. Try searching too as I know it has been discussed on which pins to match in the connector, and the value range you should get.

If you get one, make sure it is for your 3.0 version. I think the one on ebay will suit you, as I don't think OZ got the 3.0 24V SOHC version. Over here we did in 95-96. I ordered an ISC from a shop that rebuilds them here. Se sent me one that was for 3.0 12V. He didn't know there were other 3.0s in Monteros.

Eric

I read your thread, thought about posting my problem there, but as you had solved your problem I decided to start a new thread. I checked dsmisc.com, even with the $=ú rate as it is the Aus works out cheaper. I emailed the seller & he has confirmed compatibility. Which screw are you refering to, do you have a picture ? just in case I decide to try that test

MontyMcV

I pulled the ISC Wed evening, by tourch light, all the coil resistance values were good (between 28.5 & 29.4 ohms) cold, the truck has not been used for a while. I knew I had an idle problem just never got round to chasing it as the truck has not been used, there be a lesson I should have chased it when I has the truck off the road. <img src="/forums/images/graemlins/frown.gif" alt="" />
I chanced a throttle body off ebay a couple of weeks ago (ú10 inc P&P <img src="/forums/images/graemlins/kewl.gif" alt="" /> ) but it's from the later years (96 onward) so the ISC is different. The hoses too are run different. Anyone know if that throttle body will be OK on the 93 engine??

I intend to try & check the coil values on the truck, after I get home from work.

Hi Steve,
Another test to try would be to unplug the ISC and run the engine and see in the problem is still there. My own truck has an idle issue and it is not the ISC.

Charlie,

Thanks,
As I understand it if I unplug the ISC, when cold before I start the truck, the idle should remain @ the same level from cold to hot when running. If I remember correctly the ISC does not throw a error code when faulty so dissconnecting shouldn't show a code. If that works then at least I can stop using my left foot to brake while feathering the go peddle to keep the engine running while I wait for the replacment to be delivered

Steve

Not necessarily, the cold idle speed is controlled by the wax element next to the ISC not by the stepper motor. The actual idle speed should be set by the BSS as mentioned previously. There is also allot of ignition timing change by the ECU that many times is the cause of unstable idle speed.

Sounds like the ISC is porbably okay. If needed, you should be able to switch the pintle ends on the two and put the 95-96 one into your yours. At least, I did the opposite of that when I got the earlier version mentioned above.

I don't have a picture, unfortunately. On my '89, the idle set screw is covered by a rubber plug on the top of the throttle body near where the vacuum lines plug in. The FSM has an illustration, and if you don't have a copy, I believe you can find a zipped version on MontyMcV's http://www.afabot.com/ site.

Besides checking the coil resistances, see how much play there is in the pintle when you try to (gently, between thumb and forefinger) rotate it by hand. My old IAC was very loose, and the new one had no play in it. My understanding is this wear can also effect how well the ECU can adjust the IAC steps. The coils on mine were all in spec, yet the ECU could not adjust it to bump the idle up when the A/C compressor kicked in. A new IAC cured that.

Eric W.

Running with the ISC disconnected tends to burn up the driver transistors in the ECU & may daisy chain to other failures. I sold many Mitsu ECU's to peeps that did the 2 foot driving scheme withj burnt out coils.

Ed