shep28

iTrader: (4)

I am confused. I have HP and figured that I could smooth out my idle through tuning rather than drilling the TB blade. I riveted the TB blade hole which I had drilled previously before getting HP tuners. I read both of the idle tuning directions below and now I am confused. Which one should I use to get the best idle?

I have my 231 cam tuned for a 850 idle. When you adjust the tb screw, the idle either increases or decreases. When followed direction #1 step #2, my Throttle position showed 2% on my scanner when I plugged my TPS back in. Shouldn't it read o%. Adjusting the screw changes the idle.

I think this is what I should be shooting for to get a good idle:
TPS voltage should be .4 at idle
desired IACs should be as close to 40 as possible for a cammed car like mine
throttle position should read 0% at idle on the scanner or should it read 2%?

Which one of these should I use?

#1
Directions to set TB set screw

Instead of drilling use the set screw on your throttle body, and here is how:
1) Hookup Autotap or your diagnostic tool of choice. You will want to monitor your IAC, Idle Speed (and desired idle speed if you don't know it), and your Throttle Position.
2) With the key in the ON position, adjust your tb set screw until your Throttle Position is 2-3%. You can do this all at once, or gradually in 1% increments if you like. (I started with +3% and ended up adding another +1%).
3) Turn your key to the OFF position.
4) Unplug your Throttle Position sensor.
5) Turn your key to the ON position for a few seconds, and then OFF again.
6) Plug in the TPS (don't know why nobody caught me forgetting that step) and then turn your key to the ON position and restart Autotap. Your Throttle Position will now be reset to 0 degrees (or really close like 0.4%, the point is it is now reset).
7) Start your engine. Autotap is unable to pull IAC counts from my computer, but you can watch the Idle Air Control Airflow in grams/sec. A stock vehicle should show about 20 grams/sec, and that should probably be your target. I overdid it a little myself with the extra 1% to reduce the amount of control the IAC valve has over my idle. My grams/sec is between 5-10.

I wish I had measured the IAC airflow before the change, but I just wanted to get the thing to idle better. You will probably see much much more than 20 grams/sec if you Autotap it before the adjustment.

Basically the point is that you CAN adjust your throttle body with the set screw withough messing up your Throttle Position reading. WOT will still be between 99-100% (perfectly normal). And you will now have an idle that doesn't go too low. If any of you guys have anything to add to this, please do...or if I have made some error in doing this.


#2
directions to set idle-

Heres how I basicly do it. Perfect idle everytime.

-Start off with getting the car to idle, then check your ltrims, put those in line first.
-Make sure you want to idle your car at about 900-950 for a cam because it will idle so much cleaner.
-Go to all your spark tables and set the park and drive idle vavles in that area to about 22 degrees.
-Then after you have all that going, switch over to something that lets you see IAC counts and your TPS voltage. This is where you have to spend some time on it.
-Make sure your counts are between 40-60 for the IAC. This is a good amount for cam cars. Considering the stock cam runs at about 60-80 counts sometimes. The cam car will want less counts.
-To acheive this, shut the car down, raise the idle set screw up alittle, then unplug the TPS, turn the key forward for 30 seconds, turn the key off, plug TPS back in, then start the car.
-Now go back to scanner and look at your counts. Keep doing this till you reach your goal. It will take you about 4-6 times till you get where you want, but I promise you will like the results.
-The last thing to keep in mind is you cant have high voltage on TPS sensor or else the car will fall into the wrong cell at idle. So make sure everytime you change the setscrew, you fix the voltage. No more than .4-.6 I would say safely.

Another thing to help also after those changes are made is the VE. Go to cranking VE table, times the whole table by about 80% to lower it, then go to your primary or secondary if you have it, and drop about 3-6 counts off the idle area on your VE table. This will give you a nice stable idle and start up as well.

Another_User

The set screw adjustment is so you can drive the car if tuning is not available to you, or until you tune the car. Additionally, you use the set screw instead of drilling because after a cam it is very easy to max out your IAC counts, so you can put yourself back into where the IAC can adjust. It is a lot easier to adjust the set screw close to the stock table and nudge the table into place from there.