Resolved Idle Surge -- Single pin connector?

[thereef]

Edit: This is a 1g 6-bolt, don't know if it matters.

Hey guys, just trying to get some information together to try and solve my idle surge. Everything I've read has pointed to the ISC, but from what I can gather that is the larger plug located on the underside of the TB. When I disconnect the large multi-wire plug, nothing happens.

However! When I disconnect the single-pin connection above said multi-pin connector, my idle normalizes out at about 1300RPM.

What the hell is this single connector pin at the top? Is this still the ISC? Someone educate me please.

Thanks guys!

Edit: After some more investigation I've found out that it's called the "idle switch" -- still not able to put together why having it connected is making my idle fluctuate.

Edit edit: Sounds like I may need to ground my TB. Will do that this evening and report back with results.. If you have any more insight don't hesitate! I'll take all the information I can get.

 

[93TSI_370K]

On my 93TSI, there is a small 90 degree bent "grounding" strap that is fastened with a small screw to the top of the TB and the other side of the strap goes under one of the bolts that fastens the TB to the manifold.

This bolt, and the one directly below it on the TB, go through a cast iron bracket, to which the other end is fastened to the cam position sensor on the head. As the TB is sandwiched with gaskets, it is actually isolated from ground as the only other thing connected to the TB is the accelerator cable and that is a covered cable and not a good ground connector. This is how a good ground connection is maintained in order for the idle switch to function.

 

[eagle93tsi]

By your description I think you are disconnecting the single wire from the throttle closed switch. Disconnecting this will cause the idle speed to go up.

I went through this as well and found this post really helpful. Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge) What you are doing is covered in step1 of the diagnosis procedure.

In my case the issues were bad ISC, leaking injector seals, holes in the inter cooler at the hose connections, clogged EGR valve, throttle shaft seals and BISS seal. I had the throttle body rebuilt by Throttlebodys.com to solve those leaks.

Getting or making boost leak tester will help isolate the boost/vacuum leaks. good stating post http://www.dsmtuners.com/forums/art...st-how-boostpro-net-tester.html#post152554139

I also had a poorly installed timing belt that had slipped as well. Check your base timing.

One other test to consider doing is a compression test.

Checking the ISC is easy and may be your issue. This was the first thing I did and putting in a new one helped.

 

[steve]

The real question is why does the car try to run at 1300 RPM with the throttle closed.

The IPS (Idle Position Switch) is telling the ECU the throttle is closed which causes it to look at the engine speed and say "Hey, this is too high for when the throttle is closed" and shut off fuel. Then it sees the RPM drop to where it has to turn on the injectors to keep the engine from stalling, the RPMs rise again and it starts all over.

Fix why the engine wants to idle fast and the surging will go away. That usually starts with figuring out where the extra air is coming from.

 

[thereef]

Update: I've let the car idle for roughly 10 minutes, and it would take forever to stop fluctuating, then rock a steady idle at 1300, then bring the idle down in steps (1300, 1100, 950, 800) to a solid 800. This is with the idle switch plugged in.

Still looking for tidbits of information. I appreciate your guy's posts, I'll start running through Terry's list.

 

[thereef]

Hey guys, just wanted to say that I did the FIAV block in this thread (http://www.dsmtuners.com/forums/articles-intake-exhaust/391977-free-fiav-block.html) and it fixed my idle surge. Hope it helps someone else too!