2G Idle surging causes and solutions?

[JKhaphora]

So I just got my 2g dsm running good, so I drove it around my neighborhood and every time I came to a stop the idle rpms would go crazy (1000-2000ish). After some reading alot of people are saying it could be my B.I.S.S or my idle stop senser. I have no clue what those are and how to fix them.
And I don't know if you need this info but it seems important so I'll add it. I have a ECMlink V3 and the previous owner put an aftermarket throttle body (skunk pro 2).
If there is any important info I forgot to add just ask.

 

[1990TSIAWDTALON]

A 2g DSM doesn't have an Idle Stop Switch (Idle Position Switch), it is built into the TPS (Throttle Position Sensor). That switch is a 1g thing.

You should build a vehicle profile so we all know what kind of car and what all has been done (or not) to it. You can make you profile HERE.

Add any components that are not stock to your profile so we all know what you are working with and welcome to the forum, always glad to have new members!
Marty

 

[JKhaphora]

Ok thanks there's alot of things I don't know about the car I'm still trying to figure everything out, but I'll try

 

[1990TSIAWDTALON]

You definitely came to the right place! This is the BEST DSM FORUM there is, you won't find a better or friendlier web site. We all try to help out and also don't put up with BS, that all takes place on things like FB but not here.

 

[dwb]

The cause is usually too much air bypassing the throttle plate. It could be a few things (but not limited to):
incorrectly adjusted or missing BISS/o-ring
ISC/IAC not working or leaking at the o-ring
Vacuum/boost leak - perform a boost leak test (assuming GST/X) and fix any that you come across. Pay particular attention to vacuum lines, brake booster, PCV valve/line, throttle body gaskets and seals, injector seals
Throttle plate not closing - either the cable is too tight or something is binding up
FIAV (Fast Idle Air Valve). These tend to deteriorate over time and are often blocked off

Unfortunately I have no info about the throttlebody you speak of so this is based on a stock setup.

 

[khaphora]

Hi! I’m the dad-half of this project car. I posted a log in the newbie forum. https://www.dsmtuners.com/threads/2g-first-ecmlink-log-idle-issues.545456/

Regarding the leak test, I have a smoke machine and had already cleared up all the leaks the last owner left behind. The TB has one adjustment screw on it, it’s fully turned CW, if I go CCW at all it’s causing idle to go up. There are two vac lines on the top, not sure how they play into this (there is a third factory line in between them so I guess the stock used all three?) The revving feels very “feedback loop” to me, not sure if that makes sense but just a gut feeling.

I’ll go through these suggestions and see what comes of it. Appreciate the kind words and I look forward to paying it forward once I get a little more knowledgeable. I’d love to go back to mostly stock and start fresh but tbh I keep finding new things they changed (just now noticed the harness on the IAC motor was re wired so now I need to investigate why that is a thing)

 

[khaphora]

Update, pulled the IAC motor, carbon build up on the plunger so I’ll clean that. Also the oring is missing completely so.. yeah. I might just go back to stock for this whole setup. I’m not even sure what car this iac came from, doesn’t seem to match what I’m finding online for stock 2gt

You must be logged in to view this image or video.

You must be logged in to view this image or video.

 

[steve]

Looks like the skunk2 pro throttle body uses a different (Evo) type of IAC that the normal DSM one. The pintle is quite different. Here's a DSM IAC/ISC.

You must be logged in to view this image or video.

 

[khaphora]

Yep. And the pintle (thank you, new word for me) is slightly damaged where it looks like it was dropped, perhaps messing with the mixture. Anyway I’ve got a stock setup inbound with the factory sensors. I’ll give the current one another shot cleaned and with the appropriate gasket/o ring first. They rewired the harness to accommodate this so it’ll be easier to at least test it before going back to stock. I’ll update either makes a difference.