It never stops...Story AND ISC Question...Please Read

Hey Guys!!

It never rains...in freaking POURS!!!

After I got my oil pressure thing worked out, I went for a drive to the border to pick up a bunch of gear. All of a sudden my temp gauge shot up, so I pulled over.

I was just standing there, looking under the hood and coolant started to just flow out from somewhere. (Now, in case you don't know...I blew my last motors head gasket, and all of these symptoms were identical to that situation). So, needless to say, I was very very unhappy, especially because I am supposed to go to Virginia in 17 days!

So, I drove the car in to a small town about 2 mins away, borrowed a hoist and found that a hose was just not properly secured, so I threw on a hose clamp and all was well...that is my story.

NOW...

My car is doing the legenday DSM reving issue (DAMNIT). It doesnt do it that often, just when I start it up after it was sitting for a while. So, I assume that this is ISCM. I didn't think that these were that expensive, but someone told me that it was like 400 bux (CAD) from a dealership, and 300 elsewhere. I really hope that this isnt the case.

Is there anything else that this could be? I am rather doubtful.

Please let me know what you think and where I can score a new ICSM, that would be wonderful!

Thanks!
Alex

any thoughts? suggestions? questions?

Are you talking about how when you give it a little gas then the RPMs keep going a few more before finally falling? That annoys the hell out of me, I need to find a fix for this too.

Check your Throttle position sensor. Fixed my surging.

What did? cleaining it? replacing it?

Use an ohm meter and test it, if its bad get a new one. I got a new one.

TPS will only affect idle on a 2g, just for the sake of getting the info out. On a 1g, there is a seperate closed throttle switch. I have posted in the past about this extensively, but a brief overview of the parts or problems that can cause surging would be ISC, FIAV, BISS or BISS oring, vac leaks, throttle closed/TPS (1g/2g) failed or poorly adjsuted, throttle cable tension, fuel problems, etc.

Most of the time its not the ISC, but something else like imporperly set BISS, or vaccum leak. Which is good, because these things usually dont cost money to fix.

In your case it only does it when its been sitting, so I'm assuming it does it when the FIAV is open, bypassing too much air. Could be a vac leak or throttle closed switch. Check those before assuming its the ISC. Check either the vfaq or www.crebotech.com for info on how to test the ISC. In fact, the crebotech site has shitloads of info on the idle speed control system now that I think about it. Follow some of the links at the bottom of the page, if they are still there.

That is great to hear. Thanks Kevin! I will check that out and get back to you.

im realy happy now cause i have a spare one of those thanks alot kevin and big hauns that is the thing that I asked you if you need thats kinda funny.

TPS will only affect idle on a 2g,
:nono:
It affected the idle on MY 1g.

i changed the TPS and now my car idles at 5 grand (just a little high) I am going to go back over it alltonight when I get home from school but i just did my engine swap so im going to let it idle for a couple of minutes and see if it goes down.

i rep-laced the tps sensor had it idling at 5 grand but noticed that some cable was out of its slot, put that back in and ahere we go again 1 grand 1 1/2, 1, 1 1/2 i have a feeling its the ISCM.

:nono:
It affected the idle on MY 1g.

I still can't see how that is possible. I'm looking into on DSMlink forums.

Okay...I got a new ICSM (i forgot I had one off of my new motor when I did my swap) and i put it on...it still did the gay revvy thing.

What should I try next?

Setting the BISS properly? It involves grounding some pins to get the ECU to stop interfering with idle speed. I'm not sure if it holds the ISC at the center of its travel though like the scan tool does. The point is to set the BISS with the ISC centered so it has maximum range in both directions. Much like the way we set the AFC so the ECU has trims centered, with maximum adjustment range in both directions. Contrary to popular belief, the BISS is not there to set idle speed, so many poeple mess it up thinking it will adjust the idle. It is there solely to set the position of the ISC. Only the ECU has control over the actual target idle rpm.

With DSMlink, I can lof the ISC position as "Learned Idle Adjust." Centered is about 144 (IIRC). So if the ISC is opened to far, open the BISS to compensate. Etc. Not sure if any 1g loggers can display ISC position. Scantools can at least.

Seems like a lot of typing just to cover the BISS. Shows how complicated the idle speed control system can be. But you have to start working on these things one at a time to rule them out, rather than just throw money at the car randomly like some people do.

Not sure if I mentioned it above, but improper throttle cable adjustment is also very common. In a thread titles as such I described the best method for adjsuting it. Might be worth doing it just to be sure. The cable exapnads and contract with temperature changes and can easily have you chasing your tail on idle problems.

From Dave Mertz of the DSMlink forums, the 1g TPS shouldnt affect the idle speed control system. Dave is one of the two creators of DSMlink, probably the two most knowledgeable poeple on the planet when it comes to DSM ECU operation (excluding the mitsu engineers that created it of course). This makes me wonder why it helped in your case RSLaser. Are you sure you didnt inadvertently change anything else at the same time?


The 2g sensor includes the Throttle Closed switch signal (2g TPS has 4 wires, 1g has 3). If TPS is more than 1 or 2%, it will also make the ECU believe that the throttle closed switch is open, meaning the throttle plate is open, which will tell the ECU to not bother with closed loop control of the idle speed control. On a 1g, there is a seperate switch for this, on the firewall side of the TB right on top. This is another good thing to check on a 1g. Be sure the switch is closing when the throttle plate is closed. It is adjustable, and I believe the factory manual calls for turning the switch body in until the switch closes, then another 15/16th of a turn. Use a multimeter to test the switch. I beleive it simply grounds the single terminal on the top of the switch to the TB, so it is easy to test. If that switch fails or falls out of adjustment, closed loop control of idle will be eratic at best, probably impossible.

could it be that the timing is off. I heard if the idle is set to low that it surges like that.

I am somewhat doubtful of the timing, and my idel is set perfect. It was fine and then all of a sudden it wasnt so I know my idel is okay.

I found that with the ISCM I put in, the revving would not stop it would continue on. With the one I had in before it would rev up and then just stop after about 5 mins and would only do it if the car had sat for a while.

With the other one, it would constantly do the revving thing which leads me to believe that that ISCM is worse than the other one. Would this also mean that it is clear the the ISCM is the problem? Or could it be something else?

thanks!

I talked to a mechanic and hes going to hook a computer up to my car on monday or tuesday and ill poast the results then.