tweecer--setting idle

You are right, the idle page could use some clarification - anyone super knowledgeable feel free to edit it up, otherwise I'll take the discussion from this thread and clean it all up.

On the three 5.0s I have messed with the idle on, I have been able to set the neutral and drive idle speeds and the car would idle there - the ISC is what does this for you - if your ISC is already at the edge of its adjustment, however, it won't be able to allow enough air in to hit the desired RPM.

On the wiki there is an ISC adjustment link.

The jist of setting your idle higher is that you will unplug your IAC and SPOUT so that the EEC cannot hose around with the idle by adjusting the timing or IAC. Then you MECHANICALLY set the idle to around 122RPM less than desired. Datalogging to see the idle rpm while you are setting the TB will help you get it spot on, the tach in the car is innacurate for fine tuning like this.

Then plug your SPOUT and IAC back in and the IAC valve should now be able to get your idle to where you set it in the tune.

Like any good thing with the twEECer, this is only the tip of the iceberg. Once your idle is set, you need to calculate the new TB airflow If you've got EEC Analyzer, Clint goes into great detail about setting up the TB airflow and ISC and also does all the calculations for you. There are also calculations of the ISC.

EEC Analyzer's documentation says it like this:
Adjust the idle screw on the Throttle Body (TB) all the way out allowing the throttle plate to fully close. Now turn the idle screw in just until it touches the mechanical linkage. Finally, turn the idle screw in one full turn. This will place the TB plate at the correct location. If you are using a cam that requires a higher idle than stock, then adjust the TB set screw to achieve an RPM 122 less than the desired RPM.

For those that have an atomatic - there is a setting for the decay rate in there as well - how fast the idle drops going into gear. I had an idle dropping/dying issue when I put my Cobra Intake on with the automatic going into drive. I ended up putting all sorta research into idle stuff, probably more than any one human should ever do.

Anyone else have any thoughts on this? I'd like to get a good document going once and for all on both the mechanical and EEC adjustments.

Wes

does this info still apply if your running a fox TB? i'm a little confused at what method to do because of the fox TB and sn95 computer combo.

The Fox TB will have the same adjustments on it.

There is another twEECer setting worth examining as well - "ISC max RPM in drive" - this is a roof on the maximum idle speed the IAC can obtain - raise it above your desired idle speed.

Stanger007 said:

The Fox TB will have the same adjustments on it.

Click to expand...

ok. i wasnt sure if i had to adjust it the same.

Another method of setting idle that Clint hints around at and that I've seen in Don's SCT training videos is to lock the injector duty cycle at 35% in the tune and then adjust the TB set screw to achieve the idle that you want then set the ISC D/C back to stock.

This involves setting the ISC DC multiplier to 0 and adder to 0.35 and resetting the KAM.

Cars with a stock cam usually idle at around 20. Anything less could indicate a vacuum leak.

I plan on trying the ISC DC trick on my car at some point - I got it set to the correct percentage doing all sorts of crazy math, but this other way sounds a lot more foolproof and quicker.

Wes

wow fantastic thread guys.

Neet trick with the forced .035 thing. I am starting to get at idle now that it looks like the bugs are worked out. The idle is really solid just sometimes it dips alittle low/I think its set alittle high (IMHO, 850 commanded seems alittle high) and I want to go threw it and set it up for sure so I am not guessing. But really great specific info. I would like to get it down to 800-825 steady if possible.

Does anyone have the stock idle air screw settings? I want to say it is something like bottomed out and then back out a turn and a half? I can't' seem to find any hard documentation on this in my shop manual however.

EDIT: The stock TB setting is 0.01 gap between the set screw and throttle arm then another full turn. Still looking for idle air setup.

blksn955.o said:

wow fantastic thread guys.

Neet trick with the forced .035 thing. I am starting to get at idle now that it looks like the bugs are worked out. The idle is really solid just sometimes it dips alittle low/I think its set alittle high (IMHO, 850 commanded seems alittle high) and I want to go threw it and set it up for sure so I am not guessing. But really great specific info. I would like to get it down to 800-825 steady if possible.

Click to expand...

The injector timing will really smooth out an idle - I've had good luck with EEC Analyzer's calculations on that.

Then of course if you've got longtubes there's the issue of them getting cold at idle... lol. Lotta crap to think about. Luckily it's all just fine tuning once you get the mechanical adjustments made.

Wes

Stanger007 said:

The injector timing will really smooth out an idle - I've had good luck with EEC Analyzer's calculations on that.

Then of course if you've got longtubes there's the issue of them getting cold at idle... lol. Lotta crap to think about. Luckily it's all just fine tuning once you get the mechanical adjustments made.

Wes

Click to expand...

+1 on the inj timing smoothing out and stabilizing your idle

Mine had too much lope before I worked with those settings.

It really made a nice difference :Word:

Grady

On the bleed screw I have always heard like 1.5-2.5 turns from closed/bottomd' out.