Idle help, new IAC, BISS screw bottomed out
 

So I had a cold start issue where the car would fire up fine then after few seconds you would have to blip the throttle for it to keep running then it would run/warm up fine.

Got the new IAC in. car started up cold fine and kept running. My tuner Tom@TScomptuned adjusted the BISS as to mask the problem for the time being before I got the new IAC in.

So now I am trying to adjust the BISS screw with the actuator enabled in evoscan and in operating temps and everything was going smoothly until the BISS bottomed out and it wouldn't screw in any more and the idle at that point was 1500. The target idle the car is tuned for is at 1100. Now when I disabled the actuator the idle settled around 1300 which makes sense since its the middle ground between 1500 what I could set the biss to and the target idle which is 1100.

What to do now?

Check the biss o-ring and boost leak test

Yup, check for boost leaks first. Sometimes those o rings can have tears in them that cause minor vacuum leaks. If that doesn't fix it, check to see if you PCV valve is actually shutting under vacuum (should show itself during the boost leak test). The last thing would be pulling timing in the idle cells.

Tom checked for boost leaks and fixed all that I had mainly in the throttle body shaft seals but since I have put in a new UICP with a Tial bov in so Ill check for that. I tightened it pretty hard and its showing the same vacuum as before I took it off. Ill check nonetheless

Going to order a new BISS asap. I pulled the old one out and there were few small tears in in but that might of been due to me pulling it out. My dad and I had to fight it a bit lol

Put a new PCV valve last week from STM as well so there is a very small chance its the PCV.

Tom's test honestly means nothing ,since you've done work since. Do a leak test. If all is well, replace the BISS screw o-ring. I just had to do the same thing. Those o-rings are really old ,so I wasn't surprised that it had to be replaced.
hopefully that fixes you up!
{thumbup}

Are there any procedures when doing a boost leak test on a speed density set up? Or is it just pressurize the system? I know on maf you have to plug some lines on the boost controller. If someone could explain or link me a thread that would be awesome

My BISS screw should be coming in tomorrow and I will also be making a boost leak tested tomorrow as well

No difference in procedure. The MAF isn't involved in a leak test..

You're looking for post throttle body leaks. So changing the UICP won't matter for the issue you're having. You could remove the UICP and start the car and still have the problem you're having. You should do another leak test, but you're really only looking for looking for leaks post throttle body. So, stuff that on the intake manifold. Your new BOV could have a torn diaphragm, but that's unlikely, and you had this issue prior to installing that.

Before with the broken IAC in the car idled around 1400 with the biss screw adjusted to compensate for the broken IAC. I put in the new IAC in and the idle sat at 2000 with the biss screw adjusted for the broken IAC.

I adjusted the BISS with the SAS actuator enabled but it bottomed out and it went down to 1500. The target idle is 1100 so after turning the actuator off it went to 1300

And no vacuum leaks?

I have not tested it for boost leaks yet nor did I get the new Biss screw, it should be here tomorrow hopefully but with USPS you never know.

The only boost leaks could be at the new UICP I put in or the tial BOV meet point with the flange but I tightened them pretty good and don't think the vacuum at idle would be enough to pull air through a leak on a coupler thus effecting the idle. I have not touched anything else since Tom boost leak tested it.

Maybe the oring on the biss got torn a little once it was moved after 15 years of it being seated. I will be able to tell once I get it though.

Hopefully the BISS comes in tomorrow and then I can do the boost leak test. What lines do I pinch off again? I am on SD and gave the 3 port grimmspeed boost controller.

The new IAC did get rid of my cold start issue I must say.

A vacuum leak, not boost leak, though a BLT could help.you find some. If you have a loose vacuum line after the TB, you might not find it during a BLT.

Assuming there is no mechanical issues e.g boost or vacuum leaks.
I was having a similar issue but the inverse, i opened my BISS screw and couldn't get idle above 7-800. The way i resolved the issue in my scenario is add more timing in idle and fuel ( i also didn't have enough fuel hence why i had to adjust it). Normally if you're having issues with idle and cannot either decrease or increase it to desired position you'll need to adjust timing. Have a read through this thread https://www.evolutionm.net/forums/ec...cv-tables.html , this post explains all the items for start-up and idle. See how you go and let us know. :)

Yeah that might actually be it. Went far enough in my conversations with Tom and he did say he adjusted the map a little to compensate for the broken IAC

Just got the BISS screw in. Here is a comparison picture. You should be able to tell which one is the new one without a problem lol


https://cimg2.ibsrv.net/gimg/www.evo...f77cadd337.jpg