ben73

I'm having trouble working out the difference between these tables with a 7747.

IAC vs Coolant Temp
&
RPM vs Coolant Temp

Does one override the other, or are they each used at different times?
Ben.

brennanw

It's my understanding that IAC vs CT is used at start up and when warming up in Open Loop. Once in Closed Loop the ECM takes over the IAC to control things such as idle RPM.

The RPM vs CT (aka Target Idle RPM vs CT) is used to set the target idle at a give temp. I believe this table is only used in Closed Loop and for this table to work properly you have to set your base idle by:

A. Turn on ignition but do not start the engine.

B. Jumper A & B of the ALDL as if you were checking ECM codes.

C. Wait 30 seconds and then remove the plug from the IAC motor.

D. Remove jumper from ALDL.

E. Start engine and adjust idle speed with adjusting screw at throttle lever (there may be a cap covering the adjusting screw that will need to be removed and discarded).

F. Shut off engine and disconnect battery for one minute.

G. Plug the IAC connector back in and then reconnect the battery.

H. Start engine and check for proper idle speed.

Grumpy

There's IAC reset position.
IAC park
IAC vs coolant.

IAC park is where the IAC parks at.
When you turn the key on that position.
And during crank

As the engine first fires, the ecm looks at the coolant temp, and as the engine speeds goes over 400 rpm from having been on the start, the IAC closes to the IAC vs coolant count.

From there it looks at the commanded idle speed to see if it needs to add or subtract counts to acheive that idle speed.

RPM vs coolant is what you want the idle to be, at various temps..

ben73

Thanks Guys, that makes it alot clearer!
I just built a 383 for my Crossfire Vette with AFR195's, 216/220 roller, X-Ram, 2"TB's and 90lb injectors, controlled by a 7747. I only started the motor yesterday and am having a bit of trouble getting it to idle smoothly. With that info, I think I have a good chance of getting it right today, Thanks.
Ben.

Grumpy

Go slow, take notes.
It'll take some time to get the one ironed out.
Hope you have a good scanner.

ben73

Thanks Grumpy,
I use WinALDL as a scanner....
Ben.

ben73

Ok, I really need some help with this now. This is the story thus far ;-)
I have a high idle problem. I am wanting an idle around 750, but cannot get it to control below about 950. I have proven there are no vac. leaks by seating the iacs and shutting off the butterflys, this will stall the motor. I have the butterflys adjusted so that the motor will idle around 450rpm with the iacs seated. If I set "max iac retract' to about 25 counts, it idles where I want it to ~750, but of course this is not controlling the idle, merely limiting movement of the iacs beyond 25 counts.
I have systematically experimented with every idle and iac parameter using tunerpro and have not seen the iacs attempt to close off any more than about 50 counts (900-950rpm), this is when the "max iac retract" is set to about 80, so it is controlling about that 50 point, but won't shut off any more to meet my desired idle speed!!!!
I have set the iac vs temp and temp vs desired c/l idle tables rediculously low and have tried the kickdown at all sorts of different numbers also, both greater and smaller than in the iac vs temp tables. I have set the stall saver low enough so it will not kick in. Its not the a/c iac increase.
So in summary, when i set the iac max limit high (~80), the iac stays around 50, so it doesn't max out to the limit, so it is controlling to some extent. It seems the only parameter it really takes any notice of is the 'max iac retract', if i set this to 25, the iac does not open beyond 25 and my idle is where i want it, but obviously it not 'controlling'.
My TPS is set correctly and the "%tps for closed throttle" parameter is set to 3%, so it is considered 'closed'.. vehicle speed is zero thru out these tests also.

So what other parameters/tables are keeping my iacs around 50?

Thanks for reading the long post, I try to give as much detail as possible to avoid questions back and forth etc.

Regards,
Ben.

RBob

iTrader: (1)

From the man of few words:

https://www.thirdgen.org/techbb2/sho...hreadid=224960

RBob.

ben73

Thanks RBob,
I'm guessing you are referring to this statement:

As for the KICK DN ADJ STEPS, it is the key for the ECM being able to go into a closed loop idle. Until the steps in the IAC MOTOR POSIT vs COOLANT table are less then the kickdown steps the ECM will not go into a closed loop idle. As the engine warms up the row in use of the IAC MOTOR POSIT vs COOLANT tables changes with it.


I have tried the kickdown steps at all values, greater and smaller than the corresponding point in the iac vs temp tables.. 'll go and try it again just to be sure...
Any other suggestions?

RBob

iTrader: (1)

Try resetting the ECM by removing power from it (for about 10 seconds). There is a bunch of IAC info that is stored in NV RAM.

Then set the kickdown steps to one greater then the IAC Position vs Coolant at the coolant point where you want controlled idle.

The TPS may also be a problem. 3% is usually enough to make sure the ECM thinks it is in idle mode. Can always increase it temporarily for a test.

RBob.

ben73

Thanks, I'll give it a try!
I looked at a few stock bins and see the common relationship between the kickdown and the iac vs temp.
Ben.

ben73

Ok, I'm still having big trouble with this. I have tried so many things to determine what is holding my idle up high.
Here is a snapshop of some of my parameters from Tunerpro.
I'm not exactly sure of the function of the 2 at the bottom left, does the engine speed have to be between these parameters before it will enter closed loop idle control? I understand that this 'closed loop' has nothing to do with the O2 sensor etc, we are talkin about CLOSED LOOP IDLE CONTROL, not closed loop fuel control, ie it is controlling the idle by manipulating the iacs to eliminate any 'error' from the desired speed.

I have set the %TPS for closed throttle a little high to eliminat any potential probs there.

It looks as tho it is totally disregarding the IAC Posn VS Temp table, becasue as I watch the temp climb from a cold start, the IAC counts do not an all resemble what that table calls for, ie, by the time it has reached 90degC, the counts should have been at 20, (but they hang around 50, which is 950-1000rpm) then the kickdown should have forced it into closed loop idle and should now be controlling at 700rpm as per the 'desired rpm' table.

SO, what other parameters are there that can make the idle/iacs stay high?? Some type of offset??

I have experimented with almost every idle/iac parameter without success, can anyone suggest anything??
Ben.

RBob

iTrader: (1)

I have saved the pic you posted (of the parameters) figuring to test bench them later today. However, there are some parameters that are not present in the '7747 ECM.

These three: Open Loop Idle On-RPM, Open Loop Idle Off-RPM, and Open Loop Idle Threshold-TPS%, do not exist. The problem this creates is that: are the other tables/parameters labeled correctly? And what locations are being changed? May want to check the parameter definition file against the hac to double check what locations are being changed.

RBob.

RBob

iTrader: (1)

Ben, in reviewing my '747 IAC notes I missed a parameter required for closed loop idle. The ECM must see the transmission as being 'in drive'. If a stick then the park/neutral input line (B10, ORG/BLK) is left open (this is 'in drive'). If an auto trans and the park/neutral switch is used then the transmission needs to be placed into drive for closed loop idle control.

RBob.

brennanw

RBob, this statement caught my attention. I have my system wired so that the ECM always thinks the vehicle is in park/neutral. I did this because I'm using a manual trans and because I'm not using a VSS and because the instructions for my Painless Wiring harness said I should for my situation (DANGER, I followed the instructions). According to WinALDL, my ECM sets the closed loop flag and shows BLM activity. What do you make of this?

RBob

iTrader: (1)

Closed loop fueling and closed loop idle are two different things.

If you have a manual leave the park/neutral switch line open. The ECM needs to see that the vehicle is in drive in order to control the idle speed via the Idle Spd vs Coolant table.

Else it just uses the max RPM allowed parameter for 'when in park/neutral'. Try it with B10 open and see how things go.

RBob.

edit: this is from the end of my 7747 IAC notes:

I'd like to list the general quals required to get to full idle control:

a. engine is running
b. vehicle is at 0 mph (zero! hardcoded)
c. tps% is less than val at $5C6 ( tps% * 0.390)
d. steps of "IAC position vs coolant - kickdown" < 0
e. in drive, or a stick tranny (B10 open)

Now idle control according to Desired idle vs coolant tbl ($60E).

ben73

Thanks so much for you help RBob.
I have found the problem, and as it turns out, I am a moron. ;-)

I have a WinALDL cable i made some time ago when I was playing with my '6026. It has the 10k resistor built in. I forgot about this and blindly plugged all 3 wires into the aldl connector, instead of just the 2 required for comms with the 7747.
As you know, the 10k resistor forces the ecm into diagnosic mode with a 1000rpm idle. DOH!!
Ben.

RBob

iTrader: (1)

Just need to wear a cone shaped hat for a day. We all do stuff like this. I am glad to hear that you have discovered the problem.

As a matter of fact I am going to add that to the list of things required for closed loop idle.

Your post also jogged some brain cells. I recall the scan tool I use kept bringing the ECM up in diganostic mode. Drove me nuts, so I opened it up and cut the trace. But over the years forgot about the side effects that happen with the diag mode.

Thanks, RBob.

Grumpy

Here at CSH, HQ, we used to constantly plug in Diacom and forget about selecting Mode first, and would do that.

I'd written a couple posts at one time about the adventures of Capt'n Dumass. ie stupid stuff I've done. ALDL mode selection was the least of the big bobos.

brennanw

I haven't had time yet to try out the system with B10 open. However, I would like to review the CL idle logic in the hac. Would you have to have a list of labels (in the ASDZ hac) for the logic that supports the info you provided in a-e above?

brennanw

RBob - You da man! I finally got some free time to try B10 open and it worked! Started on a cold start. It warmed up very smoothly and idled right at 700 RPM, which is where I have it set via the idle vs temp table. My system is still far from being road worthy but at least I'm getting closer. At this rate I might actually get to drive my truck before 2005 gets here! Thanks so much!

Wishmaster's87IROC

iTrader: (4)

Do you remove the clip before you start the engine or remove the clip after you start the engine and have set the idle speed and shut off.

I thought you are to leave the clip in when you first crank it up and set idle.

brennanw

AFAIK, yes. Remove the clip (jumper) before you start the engine. That's how I've been doing it.

Wishmaster's87IROC

iTrader: (4)

So jump pin AB
turn key to on
wait 30 secs.
remove connection to IAC
remove clip


turn key back to off and the crank motor or crank egine over from the "on" position....

brennanw

Either way will work because all you're doing in the preceding steps is driving in the IAC pintle and then disconnecting it so it will stay closed. The key step now is to remove the jumper clip before you start the engine. You can then turn the key to off if you want to but it's not necessary. Just pull the clip and start the engine.

3gen90camaro

New to the site, Step 1 set timing.
Step 2 set iac to 0,start and set the engine 50 rpm less than bin file vs ct. Step 3 correct tps angle to .5 volts. Step 4 reconnect iac clear codes the vehicle needs to enter a drive cycle 35 mph for a few minutes when you come to a stop the idle will hunt and should settle in a minute or two.
Hope this helps

bigal55

iTrader: (1)

It's great that you post this info and maybe it will help someone but, did you notice this thread is over 12 years old? Great info though!