Trying to test ISC because of bad idle. Problems.

[96gstdsm]

Well I have not driven my car for a while now, but before it was always having idle problems and all so I figured it was a bad ISC so I went to test it today and I really don't know whats going on. I must be doing something wrong.
I have a multimeter and when testing the pins, the multimeter number just goes all crazy up and down and then stops back down at 0. I have it set at 2000k. It will like go 450, 794, -14, etc (just random examples) and then always stops at -000. Am I testing it incorrectly? Or is this how it acts when the ISC is in fact damaged? please any advice would be great as I am looking to sell this shortly, and would rather sell it with a good idle.

 

[96gstdsm]

Block off the ISC and FIAV and call it a day

What will that do? How will it help fix the problem?

 

[steve]

Block off the ISC and FIAV and call it a day

That's the lazy man's solution.

 

[96gstdsm]

That's the lazy man's solution.

What would it do? Would it be a temporary fix? Want to at least eliminate things it's not.

 

[steve]

It disables the idle circuits for both. All your left with is the BISS and your right foot to maintain the engine idle speed.

The ISC has other functions than just idle, read the tech manual if your interested in them.

 

[96gstdsm]

Do you need to buy a block off plate or something? Are there any problems that can arise from doing this besides a bad idle possibly?
Can the idle stay steady without them ever?

 

[96gstdsm]

Alright I routed the coolant lines back into the throttle body and I tested the ISC which is fine. TPS read fine as well.
I let it idle for about 20 minutes pressing the gas once in a while. it idled real nice at around 800-900 rpms. So I decided to take it for a quick spin around the block. It was driving great for the first time around or so, and then when I came to a stop it stalled out. Then went back to idle at around 600 rpm's. Drove it around again and came to a stop and the same thing happened. What else might be out of wack that this is happening still? Seemed to be fine while it was idling, but I guess once I put it under load it started to stall. I do have an 8 lb flywheel and some BC 272 cams. Should I maybe try and raise the idle up more so it idles around 1000 or so normally?
I will have to do another boost leak test shortly to see if any leaks opened up since it was sitting in my back yard.
What should I check next?
On a side note, I see a bunch of oil around the CAS. It does not appear to be coming from the valve cover gasket and I also replaced that very recently and has not leaked since.
Is it a pain in the ass to remove the CAS and fix the leak? My thermostat housing is also leaking some coolant it appears. So I will have to fix that shortly.
Man the shop that did my install really sucked hard!!!!!!

 

[steve]

I do have an 8 lb flywheel and some BC 272 cams. Should I maybe try and raise the idle up more so it idles around 1000 or so normally?

The lightweight flywheel and cams doesn't help here.

You can't have an operational ISC and idle other than the 750 +- 100RPM that the ECU is programmed for.

 

[96gstdsm]

The lightweight flywheel and cams doesn't help here.

You can't have an operational ISC and idle other than the 750 +- 100RPM that the ECU is programmed for.

OK so I must be testing it wrong then. I disconnected the pigtail harness from it and then used the multimeter to check the resistance between the pins. Should I test the pigtail? Also I am a little confused on how to adjust the isc so that it is at the 33 ohms it should be at. Mine showed around 36-37. I saw somewhere about reseting it. How is that done? Or grounding it out??

 

[steve]

There are no adjustments to the ISC. It works or it doesn't but you can drive it out of range by misadjusting the BISS or by vacuum leaks. As I posted before the ECU also depends on the IPS to tell it when the throttle closed.

 

[96gstdsm]

There are no adjustments to the ISC. It works or it doesn't but you can drive it out of range by misadjusting the BISS or by vacuum leaks. As I posted before the ECU also depends on the IPS to tell it when the throttle closed.

I don't quite understand the whole IPS part. So there is no individual IPS correct? It is inside the TPS? Didn't find much of anything when searching for testing the IPS.
I had tested my TPS before and it was good. The connection unfortunately is not very good so I have to use tape to hold it in.

 

[96gstdsm]

Alright sorry for all the questions, but just really not getting the whole ISC fixes and possible issues.
Can I keep adjusting the BISS turning the engine off each time until the idle stays at around the 750 rpm's to get the isc back where it should be? Or once it get's out of wack from adjusting the BISS too much do I need to replace it? I know the BISS was messed around with many times trying to get the idling better.

 

[steve]

I don't quite understand the whole IPS part. So there is no individual IPS correct? It is inside the TPS? Didn't find much of anything when searching for testing the IPS.
I had tested my TPS before and it was good. The connection unfortunately is not very good so I have to use tape to hold it in.

Inside a 2G TPS there is a IPS. It switches on and off very early in the rotation of the shaft. This is how you adjust the TPS on a 2G by turning it and measuring where the IPS switch changes from closed to opened. This adjustment is critical to the correct functioning of the idle circuits. It's has to be correctly set before you can set the idle speed.

Alright sorry for all the questions, but just really not getting the whole ISC fixes and possible issues.
Can I keep adjusting the BISS turning the engine off each time until the idle stays at around the 750 rpm's to get the isc back where it should be? Or once it get's out of wack from adjusting the BISS too much do I need to replace it? I know the BISS was messed around with many times trying to get the idling better.

You really should find and read the 1G Technical Manual, the function of the idle circuits would the same way on a 2G. I'm not going to try and copy the section here. You need to keep in mind that there are three bypass parts that work together to set and maintain the idle speed. The FIAV, the ISC, and the BISS. The FIAV works to provide a high idle when the coolant temp is low. Once the coolant fed to it gets hot it closed and doesn't bypass additional air. The ISC is computer controlled (assuming a good ISC and undamaged ECU). It has a default position that without DSMLink requires a MUT factory tool to set so you can adjust the BISS properly. Adjusting the BISS without forcing the ISC to it's default position can cause high idle problems or cause the car to stall when you close the throttle. screwing around with the BISS isn't going to damage the ISC, just mess up the adjustments.

The engine needs to be at operation temp before you should adjust the BISS so that the FIAV is closed, you would set the ISC to it's default position with the MUT, and then turn the BISS until you get a 750rpm idle speed. Without the MUT the ECU will see the IPS closed and try to maintain the idle speed, as you change the BISS the ECU would open or close the BISS to keep the idle at 750 rpm so it would seem that your BISS adjustments weren't doing anything until you forced the ISC closed.

 

[96gstdsm]

Ok thank you, very helpful.
I would assume you can get the MUT tool from the dealership? Or other places have that for cheaper?
So it's a datalogger type of tool? Thats what it seemed like when I did a little searching for it.
That sounds like the ISC has to be the culprit right now. Just won't hold the idle up once fully warm when letting off the gas. It just won't catch it from stalling out.