Tuning 75mm TB

Dirk SC

Dirk SC

Registered User
I am trying to tune my Idle on my new TB but everytime i unplug the IAC the car dies no matter where i have the air bleed screw adjusted too or how warm the car is. How do I get it to idle in the propor spot if i cant keep the car running?
 
Just prop the throttle plate open with something, like a paper clip. Unplug the IAC and start the car. If it doesn't start with the throttle plate open even if the IAC is unplugged, then you have other problems.
 
It's a bit of a balancing act. You should be able to get the car to *just* idle or at least darn near with the IAC disconnected. You don't set idle speed with the IAC off, you just want to set up your throttle blade and air bleed so that the IAC is only controlling about 25-35% of the air needed to keep the car idling.

So open the air bleed all the way and then turn the idle stop up until it WILL idle at some rpm with the IAC disconnected.

Once you have it running that way then close down the throttle stop until rpms drop to about 600rpm more or less. The throttle stop should always be in contact with the stop by at least 1/2 turn to 1 full turn. If when it is idling down around 600 or so (don't worry if it stalls but it should be close to idling) you find that the throttle is at less than 1/2 turn past contact with the stop, then it's time to close down the air bleed and set the throttle stop at a minimum of 1/2 turn from full close. You never want a throttle blade fully closed.

Once you have gotten to that point then you need to check your TPS and set it at .95v. After that, plug the IAC back in and you will have a base idle.

Sometimes the idle ends up being too high after following this procedure. If so then you DON'T want to mess with the throttle stop, just close down the air bleed a little more.

The EEC will learn idle parameters after a little time so don't be afraid to drive it around some if it still isn't perfect. It will learn some.

Ultimately there may need to be a few changes made in the tune file to compensate for the cam you have and other things.
 
Ok good that makes a lot more sense. I set my tps to.98 and but when i was tightening it down it must have moved slightly and now sits at .99. Is that still ok?
 
Dirk SC said:
Ok good that makes a lot more sense. I set my tps to.98 and but when i was tightening it down it must have moved slightly and now sits at .99. Is that still ok?
Click to expand...

.90-.99 is the prefered range. Obviously you are on the very edge of the prefered range. There is no "right" value.
 
Toms-SC said:
Perfect, I needed this thread badly. Thanks for the post Dirk & Dave! :)
Click to expand...

No Problem. Better get that car running proporly before the tune! Thanks for the help Dave.
 
If your still using the stock throttle body, then thats a step you needn't worry about as it does not have an air bleed screw.

at least I have never been able to find one on the earlier style.
 
You must log in or register to reply here.
Back
Top