Idle surge and emissons removal

[Andrew Scott]

Idle Surge and Emissons Removal
Idle surge occurs when too much air gets through the throttle body, causing the ECU to inject more fuel, causing the the idle to rise. Once the RPM gets to 1500 rpm, the ecu cuts fuel and the idle drops. After dropping, the ECU again injects fuel, and the cycle annoyingly starts over again.

You should first use your common sense... look under the hood and listen. You are listening for escaping air. Hiisssssssssss. You have a leak! Fix it!

Idle surge can be caused by several things, mostly leaks.
Many solutions have been found, I will list them below (in order of ease to check):
1) Start by replacing the o-ring around your idle ajust screw. If you don't have an idle ajust screw, there is your problem. It is located :


2) Check your throttle body butterfly valve to see if it can completly close. Sometimes carbon buildup can stop it from closing. If this is the case, clean the throttle body with carb cleaner.
Doing this is fairly easy, it requires you to simply remove the intercooler pipes and throttle body elbow:

If you need exact instructions on how to remove it, check your repair manual, but it is fairly elementary.
Once that is off, inspect the throttle body. If it needs cleaning, carefully prop open the butterfly valve on the throttle body with a screw driver, and spray in some carb cleaner. Wipe the carbon buildups away and allow it to sit proped open for a couple of hours, so all the carb cleaner can evaporate. THIS IS VERY IMPORTANT. If you do not do this, you can hydrolock your engine. (bad!)

3) Test your ISC and your Fast Idle air valve:
http://www.geocities.com/MotorCity/Downs/7678/dsmtests.html
Also avaliable in the repair manual.
Alternatively, you can block off the FIAV:
http://www.vallotton.com/fiavblockoff.asp

4) Blockoff your EGR valve. After a while, your EGR valve can call it quits, so instead of getting a new one, why not just block it off. Very easy to do, and dispite what alot of people say, I personally think it will not adversly affect your drivability etc. You can buy EGR blockoff plates from pretty much anywhere, or you can make your own if you have a dremel.

-Remove the EGR valve from below the opening of the throttle body.
-Between the valve and the engine, there will be an aluminum gasket, with two big holes, and two little holes.
-Your main goal here, is to reproduce this gasket with only the small holes in it.
-Cut two of these from an aluminum pop can, stack them, put them between the EGR and the engine like the original gasket, and bolt the EGR back on.


5) Remove your emissions equipment. Having millions of vacuum lines is not only ugly, but it also is a huge cause of boost and intake leaks:
http://www.taboospeedshop.com/emissions.htm

Below is a vfaq on how I did this:

Pull off all the vacuum lines from the throttle body.


loop the vacuum lines back onto the nipples to seal them off, like above


pull off the lines attached to the solinoids labeled in RED. Leave the one in green!


Remove the charcol canester. It is located below your battery and battery tray. If you can't get that out, you shouldn't be doing this. One line from the charcol canester will run to the gastank, while another will run to your intake pipe. If you have an aftermarket intake pipe with no nipple for this line, it will just be hanging around in your engine compartment somewhere. Throw out the canester and this line. If you still have the stock one hooked up, pull the line off the stock intake, and plug the nipple on your intake with somthing.
Just leave the line from the gas tank hanging there. Yay! Gas fumes in our engine compartment! If you wanted to be safe you probably wouldn't drive a sports car anyways.


Remove the arrowed lines from the thermostat housing.


Here's our friend the EGR valve again. Remove any vaccum lines from him.

There will probably be some lines dangling around now, follow them and disconnect them. Most of the ones we haven't disconnected now will be attached to some hard lines on the inside of the curl on the intake manifold (strange engineering I know..), and your done. Start 'er up, and see if you missed anything. Your car should run exactally the same as before. If it doesn't you've messed somthing up.

6) If you still have idle surge, check out this document:
It may be able to help
http://www.dsm.org/how-tos/tttt/tttt3.html

[Martin Raska]

Awesome writup, but I'm going to caution people against much of that if they have to go through aircare.

[Andrew Scott]

That stuff won't affect your emissons that much... eliminating the charcol canister, lines for the purge valve won't do anything... blocking off the EGR valve will lower hydrocarbons, but rise NOx... don't know too much about NOx thogh, haven't been through aircare in a while

[Andrew Scott]

oh yeah, to lower NOx, just turn down your boost. NOx is caused by high combustion temperatures.

anyways, martins right... but who has to go through aircare anyway?  

[Kevin Standeven]

I've done everything listed there (except test the ISC and FIAV, not that it would matter) and passed aircare without a problem.

EDIT- might as well use this real estate to say, GREAT POST ANDREW

[Martin Raska]

I've done everything listed there (except test the ISC and FIAV, not that it would matter) and passed aircare without a problem.

Well there you have it.  I've just had problems with the egr in the past in another car so I would be hesitant against removing it.  It won't help emissions that's forsure but I guess you should be able to pas without too much problem without it either.  This has intrigued me now.  I'm going to look into the egr system more when I get home.

[Andrew Scott]

basically the EGR system recirculates exhaust gas back into the throttle body. (EGR stands for exhaust gas recirculation ) What this does, is stops the fuel from burning so fast and hot. Now this might sound great to us, as this would also reduce knock... but in my opinion this is a terrible way for a tuner to do it.
From a production car standpoint, it makes perfect sense, as most people don't care about carbon buildup in thier intakes, but for us, we look towards other things for reducing combustion temperatures; water injection does exactally the same thing without the carbon.

[Martin Raska]

Yeah some carb'd cars I have even seen use the heat from the egr system to further vaporize the fuel spray.  So it really isn't all that bad I just meant looking into what it's removal really leads to emission wise on our cars.  So all use aircare people can remove it too, save the environment, and run without it.

[Mike Schmid]

It doesn't really stop knock though... At least not the kind of knock we're concerned about because AFAIK the EGR is supposed to close at WOT.  I always thought the main purpose was to route non reactive exhaust gas into the combustion chamber to take up space at part throttle thereby improving fuel economy in low load situations.

[Andrew Scott]

It doesn't really stop knock though... At least not the kind of knock we're concerned about because AFAIK the EGR is supposed to close at WOT.  I always thought the main purpose was to route non reactive exhaust gas into the combustion chamber to take up space at part throttle thereby improving fuel economy in low load situations.

Really? Hmm, I always thought it was there to reroute the gas to lower combustion temperatures, and therefore NOx emissions, at high throttle.. Like I really know anything about emissions equipment other than how to remove it anyways though.

[Mike Schmid]

I remember Todd Day, the Talon Digest moderator, went into a big thing on the EGR one time.  I don't recall it exactly and I'm too lazy to look it up but the jist of it was it helps your fuel economy and except for the carbon deposits doesn't hurt your WOT.  

Now if the EGR isn't working properly or you'll take the mileage hit in exchange for squeaky clean ports then why not.

[Chris Clark]

Yes, EGR is only used at part throttle.