ICS and TPS question

Moved to Tuning.

It's going to depend upon how the idle was set. As an e.g., mine used to have a hot idle at 675 RPM with no IAC function After resetting the idle back towards stock (thanks to Wes's tune and how he redid the commanded idle in Drive gears), it will stall (with or w/o the chip) if I disconnect the IAC.

My static TPS readings are always on the high side so I can't help there. I've had one baseline at 1.21 volts but that's as high as I've been.

Good luck.

You've got enough mods away from factory stock that you will have to mess with the idle a bit. The idle settings are the toughest things to tune, hands down. Give me WOT tuning any day.

I wouldn't worry too much if the car dies when the ISC is unplugged, who drives without their ISC anyways? With the car warmed up, you should be able to get it to *barely* run when the ISC/SPOUT is unplugged with some gas pedal play, but I would not fret too much over it.

There are a dozen different ways to go about setting your idle if you have PCM access. I don't have a favorite method yet.

The instructions in EECAnalyzer work well for stockish combos, you may have to fudge them a little depending on your cam etc. (ISC screw 1-2 turns up from bottom, TB set screw 1 turn past 0.010 clearance)

Another method is to lock in your ISC dutycycle at 35% (There is an adder and a multiplier you can set to 0.35 and 1 respectively) then use the ISC bypass screw to get your idle where you need it.

Also watch out for the maximum idle speed scalars and be sure to raise them so that you are not hitting a ceiling in the computer.

Another area to watch is if the ISC is not in control of idle, the spark will be used to help. A way to cheat this is to back down your spark at idle in the spark tables to somewhere in the neighborhood of 15-25. It really depends on the combo.

And some other things to look at are to make sure you are in closed loop and not being forced rich (or lean) -- watch the LAMBSEs, they should be hovering around 14.67 give or take 0.5 or so. And make sure there are no vacuum leaks etc -- those will ruin your day.

Log your ISC dutycycle and watch what it does. Also make sure the ISC is working properly, cleaned etc.

This is some of the more common things to watch out for, but there is more (a lot more).

There is some things here that define the scalars involved in idle and your idle transitions: http://www.mustang-tech.org/wiki/94-95_Mustangs_Tuning_Idle

Good luck,
Wes

What Wes said

One thing that will cause you grief is if the tb blade is open too far

That can hose up all your other idle adjustments

Also ... cam duration (low lsa value) can really effect the idle

Speaking of cams ... if you have one start out with an idle speed of
850 or 900 rpm. Then when you get it stable ... Try lowering it in steps
of 25 rpm at a time to see what it likes best.

It took me a good while to learn this

It has been my findings if you try and find the best idle tweecs with
the idle set too low, it will make things much more difficult for you.

Here is another little trick that may help

After you feel you've made some progress at obtaining a stable idle .......

Get everything normal like ect temp, accessory load, and make sure you
have had the car operating for at least 30 mins to ensure a stable alt
output.

Let it idle for about 1 min capturing data
Get the average of the maf volt values for the 1 min of operation
See how that fits in with your maf curve

You can always tweec the point and maybe one before & after by a small
amount for a bit of fine tuning

O Yeah ... bucking at a cruise speed

If you look at a things during a very light load cruise
You will see it is almost like idle conditions
so
If you have an unstable idle ... Well ... You see where I'm going

Good Luck

Grady

The dip can probably be fixed in the ISC Transfer function and TB airflow (average MAF voltage at base idle RPM -- ISC and SPOUT out)

TB airflow is: AvgMAFKgPerHr * 2.2046226 / 60 = TBAirFlow

Wes

About the low load cruise bucking thing

Yes ... lowering spark can help with that issue

I agree with Wes about the airflow and concentrating on the scalar for the tb
and the function for the various rpm points. It makes so much sense if you
think about it. We put on parts to increase airflow ... thus ... it is also increased
at and around idle rpm's ... yet ... the pcm still thinks we are only generating the
airflow of a stocker.

You can make major improvements with these two things

I found much improvement with the isc neutral idle air flow function. That is
what it is called in the older software so I don't know if its name was changed
in the newer software or what but you see various air flow values for various
rpm points.

Grady

R100RT said:

HiYas Grady,

I pulled about 12 degrees from everything below 20% load and less than 1500 RPM. That really helped.

I'm solid on my drive and neutral idle airflow. They are easy to data log.

TB airflow is not easy to data log if the engine won't run! What I did was to guess that the engine would idle about 500 RPM with the ICS disconnected. Then I went into the neutral idle airflow and used the airflow from that point in the curve. It is pretty straight. My '65 would run with the ICS disconnected. The cam I used was better at idle than the one I used for the '94.

Eric

Click to expand...

Good to see you made progress Eric

I would like to offer some info for you to think about

You pulled 12 degrees of spark

You said it worked out well for you and thats great

Consider this my friend
SBF's have been pumping out max power for years at 36 total
give or take a few

The amount of change you made represents 1/3 of that total value
and
1/3 of anything is a substantial amount

It might be beneficial to find the threshold point of that change you made

In other words ...

Yes ...12 fixed the prob
but
Could it be

12 being such a large amount ... throws other thing out of whack

Maybe the issue could have been fixed with no more than 2 or 4

See where I'm going here

Not being critical here

Just letting you know I have made subtle changes in the past to see if
an improvement could be made. Some of those times ... I did not see
any improvement with a small change but my feeling for doing the
change made logical sense. I might make a second small change with
still no improvement. At this point in time I asked myself ... does logic
still tell me I am doing something that makes sense.

If so ... I would make a large change that might represent 15% or 25%
and if an improvement was then seen. I went back and found a value
that would make the difference of good but no more.

Just in case that did not make sense ... Lets use your application

Say 6 degrees would have done the trick
I might have done 2 the first time with no positive results
I might have then gone to 2 more for the next step with no change

Here is where I might have done like you and made a large change
and
Of course ... the desired results would have been found

I would have then gone back and found how much more than 4 was
needed to fix the prob but I wanted to know I used a value of no more
than was necessary.

You may not see the logic here
or
You may not feel the effort is worth putting into place

I just thought I would share an idea with you ... thats all

Grady