Can someone explain, in detail, how to do this?

Thanks in advance!

 

All you need to do is oversize hole in throttle body one or two drill sizes, and take throttle body set screw out from bottom of TB and screw it in from top so you can adjust it w/out removing tb each time. I set idle so car doesnt surge on hot restarts and let IAC counts fall where they may.No problems to date with a 112*LSA around 224* at .050" grind. Even ac works fine, i just shut it off before any retarts, once its running i can turn it on no problem. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

I never had any luck raising the idle like that. The computer would just learn it out or if I went so far as to make the IAC pintel position reach zero it would set a code and the IAC would cease to work.

Anyway, moving to Computer Diagnostics and Tuning... <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />

<small>[ November 28, 2002, 10:40 AM: Message edited by: Colonel ]</small>

 

Thanks!

 

I have to second that, I could not get my IAC to sit correctly with this method either. Still got SES light too due to the 112 LSA on my cam causing the lumpy idle.
I was able to get it to run better with this method and did get it to run without surging or stahling.

Without autotap or efilive it will be a real b!tch to know if your getting it to where the idle needs to be.

After LS1Edit though, its running great.

 

The good old days of turning an idle adjustment screw are gone forever. The shop manual says the idle speed is NOT adjustable. The PCM is going to try and set the idle speed at what it was told by the GM engineers. That's the job of the IAC. The only way to get around this is to somehow fool the PCM. You can open up or plug the hole in the throttle plate to make the engine run lean or rich at idle which might lower or raise the idle speed, but the PCM is going to keep trying the Idle Relearn Procedure to reset the idle speed at where it was originally told it should be. You have to figure out a way to fool the PCM or the IAC. Good Luck.

 

To expand even further...

There is a TABLE in the PCM, that contains the target idle. Drill a half inch hole in your TB, it doesn't matter, the PCM will attempt to make your engine idle at the value set in the TABLE.

For example, in an A4 computer, this value may be 550 RPMs. You will NOT be able to raise the idle to 900 RPM without programming. The PCM will always be trying to make the engine go to 550 RPM, and will adjust as much as it can (IAC) to get there.

So, to actually raise the idle, you need programming. LS1Edit or a professional tune can get you there.

One thing to keep in mind, even if you program the idle up, you may have to drill the TB blade to flow more air in to the motor at idle, to get your IAC counts in check. Ideally they should be between 40-60 at warm idle. If they're 100+, then you need to drill the TB blade to bring the IAC counts back down.

-Andrew

 

I have two friends with 6-speeds. They both did h/C packages and to set the idle higher where the car wouldn't die they just drilled a hole in the throttle body. It worked fine for both of them. I don't see why this wouldn't work. It is the same thing as barely pushing down the pedal inside of the car to open the TB. Does what you guys are talking about refer to A4 cars only? I would still think it would apply..?? Please explain.

 

If you adjust the screw, you are basically cracking the TB blade open a bit. Now you can only do so much before you set a TPS 'too much throttle code."

Now, it won't really raise your idle but it will help the car from stalling out when coming to a stop. You can try doing this instead of drilling the blade out. So the short answer is that you can improve your idle stability.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by SStolen:
<strong>I have two friends with 6-speeds. They both did h/C packages and to set the idle higher where the car wouldn't die they just drilled a hole in the throttle body. It worked fine for both of them. I don't see why this wouldn't work. It is the same thing as barely pushing down the pedal inside of the car to open the TB. Does what you guys are talking about refer to A4 cars only? I would still think it would apply..?? Please explain.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I agree...with a 230 cam my Vette couldnt idle without tuning until we drilled the throttle body...theory or not, it works.

Another trick is to create a small vaccume leak in the pcv tubing. If you poke a pencil size hole in the pcv tube near the right side head it will effectivly raise your idle and the relearn will not correct this. This isnt the smartest way, but it works.

 

Sure drilling a hole in or cracking open the throttle blade helps the idle not to surge and stall as much but it's NOT from raising the idle. It WON'T do that because the IAC will compensate by pushing the pintel in and allowing less air through the IAC thereby completely balancing out the extra air let in by enlarging the air hole in the blade or by cracking open the blade. "Well then Colonel, why the hell does it help the idle not to surge, hunt, and stall then Mr. smartypants?" Because the pintel in the IAC will be pushed further in thereby lowering the IAC pintel position counts. Due to the way the PCM is programmed the IAC will not make such drastic and selfdefeating overcompensational adjustments when the idle trys to hunt.

...But, the idle speed will still be where it's programmed to be. Autotap and you will see. You will see "Desired Idle Speed" (on my stock '02 A4 it is 650 in neutral and 550 in gear for example.) That is what the IAC attempts to maintain. If the RPM goes above this number the IAC pintel pushes in. If it goes below this number the IAC pulls out. The only way the IAC will not keep the idle at this RPM is if there is so much airflow (airhole too big) that the pintel is pushed all the way in (pintel position at zero.) (This is a good reason to drill the hole only big enough as to bring the pintel position counts down to 20-30 WITH THE ENGINE FULLY WARMED.) In this case a code will soon be set and the IAC will COMPLETELY cease to function for the duration of that driving cycle or until the code is cleared. Is this a bad thing? Yes. Your idle will be eratic. It'll change when conditions (engine temp, weather changes, etc)change. It'll be higher sometimes and it'll be lower sometimes. And it will STILL by prone to hunting, surging, and stalling.

Hook up the Autotap, drill a hole, or crack open the blade, and monitor the IAC and the idle speed. You'll see what I'm talking about. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

<small>[ December 05, 2002, 11:36 AM: Message edited by: Colonel ]</small>

 

"If you poke a pencil size hole in the pcv tube near the right side head it will effectivly raise your idle and the relearn will not correct this."

I really don't see how that's possible. You tried this and monitored your engine RPM with a diagnostic scanner? What was it before and after? ...And the IAC pintel position counts were not at zero (that would be the only way I could see the idle RPM actually changing?) No code was ever set?

Regardless of how you go about introducing more air into the engine the PCM is still going to read the correct RPM and will still use the IAC to see to it that the actual RPM and the "desired idle speed" match. I don't see any way around that and if I'm wrong I'm most confused as to how. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Yeah the PCV hole thing will work but that's not how I would do that, I think that will screw up the fuel trims. I found at this 'controlled' vacuum leak would raise the idle because part of my old pcv system was loose.

 

Hey, the Colonel ain't just fast, he actually understands how some of this stuff works! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Good job! <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" />

 

When I tried to come up with an idea on how to raise the idle speed the only thing I could come up with was that you would have to do something that the PCM or IAC would be FOOLED into thinking you DIDN'T do. That's because the PCM, as the guys that know how OBD II works have correctly said is going to keep trying to set the idle speed where the GM engineers want it to be. That was before I read about the hole in the PVC hose. Actually that method does FOOL the PCM and IAC because the PCM and IAC can't figure out the hole is there so they don't try to compenstate for it. My question is what about someone that runs their PVC into a catch can (puke bucket on dragsters and funny cars). Does their idle speed artifically go up as a result of that modification? I would guess that it must. Anyone that wants to make their street car go faster does themselves if they study and learn how OBD II works and learn to work within the OBD II parameters or learn how to FOOL you PCM and other sensor within the system. OBD II is here to stay unless the federal government bans the EPA which I don't think is going to happen anytime soon.

 

"That was before I read about the hole in the PVC hose. Actually that method does FOOL the PCM and IAC because the PCM and IAC can't figure out the hole is there so they don't try to compenstate for it."

Why can't the PCM figure out the RPM is different? It will still read the correct rpm. It'll see that it's higher than the desired idle speed and it should take measures to match the two. Why wouldn't it?

About the catch can... The answer is no. The idle speed doesn't change. I watched NineBall do it the other day and his idle was uneffected.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Speartech:
<strong>Hey, the Colonel ain't just fast, he actually understands how some of this stuff works! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Good job! <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thanks! Hang around this stuff long enough and some of it's bound to sink in! <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

<small>[ December 05, 2002, 11:43 AM: Message edited by: Colonel ]</small>