Stupid Idle Surge

[Halon]

ok well ever since the day i bought this car, it had a very little idle surge going on. Well it's gotten worse and worse. First thing I thought was maybe its the EGR, so I went ahead and did the emissions removal thing according to Taboo's site. Well it was still there, so then I tested my ISC, i got an open reading on 1 of the 4 coils. I then purchased another ISC. Put that in. Problem is still there. Then I found out my EGR blockoff plate was leaking. Thought maybe that could cause it to do it. So today i went and sealed it up real good. Idle surge is still there. Anyone have any pointers they could throw at me to get rid of this. I take the near 2000 mile road trip to MN end of May, and I'd like it to be gone for the trip. Thanx!

[A//// Guy]

Your fast idle valve is likely the problem. You will either need a new bottom half of a throttle body (FIAV) or a whole new one... whichever you find for the cheapest I guess.

That was the problem with mine.

[Jacek]

check the biss screw o-ring while at it.

[unreal808]

-Operates as Designed-
:goodluck:

[JasonR]

5 ways air passes TB: throttle plate, base idle speed screw (biss), ISC, FIAV and egr. ECU moves ISC around all the time when driving. When let off throttle, ECU steps the ISC all the way open to "catch" the engine as the RPM's fall below 1000. Now we know this. First thing to do is set the ISC. Should be done before every season or once a year, especially after modifications or when more air flow. Do this when engine is hot. I cannot stress this enough or on a hot day as well. I don't know what year your vehicle is, but you will need to ground ignition timing adjustment with jumper wire. Then the engine will run steady and ECU can't fiddle with ISC. I have 95' eclipse and its the brown connector on fire wall. Now just adjust biss until steady run at 750 or if you have big turbo HP, maybe set at 750-1000. If you have DSM link match both. Now you will have tuned ISC and disconnect ground. Now you set the correct range for ISC. You may have to replace rubber o-ring for biss. If this does not work. Then you eliminated base idle failure along with the fact you checked EGR and replaced ISC. So then it is FIAV which you will have to replace or clean the throttle body. If none of this works the car is not running correct or vacuum leak, or even bad o2 sensor which you can check by smelling exhaust when car surging. check terry's talon troubleshooting tips under idle surge in vfact on dsm talk. I must mention most of the time its just adjustment of biss when you ground ignition timing. Allot of information, sorry about that. Hope you fix.

[LightningGSX]

The transistors(inside the ECU) that control the ISC have a habit of frying also.Open your ECU and check IC107 and IC105(Black with 8 pins, up by the connector, off to the side) for damage.

[Halon]

cool thanx. i have pretty much all day tomorrow to screw with this so ill be trying to do these adjustments. I'm not sure where this ignition timing thing is that im supposed to ground out, but ill look around to try and figure it out. thanx for the replies.

[JasonR]

I should stress, you will have to ground the ignition timing adjustment to fix. Cannot just adjust biss. Pick up Chiltons book at checker or different store for your car. Your vehicle may have to be grounded different position. I hope goes well.

[Halon]

i have a chiltons for the car already. I went on vfaq and grounded the ignition timing per the vfaq. Once the 2 points were grounded, guess what. IDLE SURGE IS STILL F*$%ING THERE! This is really starting to drive me nuts. I also did what it said about checking the vacuum lines real quick. I don't have that many lines because I did Taboo's lil emissions removal. But I took off every vacuum line and put my finger over the ends, and nothing had any sort of impact. I am about to take off the TB Elbow and clean the sh!t outta the throttle body. Then if that doesn't help, the I dunno, maybe I'll just go and do that FIAV removal they have on vfaq. Also, I don't really know how to check the o-ring on the BISS. I tried just putting my finger over the top of the hole and sealing it with my finger, so i know no air could escape. But that didn't do anything. Anyway, I'm off to go clean the TB. Please keep the info coming, I'm really running outta patience with this.

[Halon]

Real quick, you said there is 5 ways air can get past the TB. Well here's what I've figured I've eliminated so far

-ISC (replaced about 30 miles ago)
-EGR (Blocked off and emissions removed as per TSS vfaq)

what's left is:

-BISS (not sure how to check this)
-FIAV (how do i check? can i just do the blockoff like vfaq and by doing this would that eliminate it as the being the culprit?)
-Throttle Plate (I'm going to clean it right now, anything else I can do to check this?)