Here's a copy of normal IAC parameters from ARAP. Perhaps something has been changed that is preventing closed loop PID.

Have you tried disconnecting the battery to clear any learned values that may have an impact? Couldn't hurt.

;======================================= =======
; IAC PARAMS
;
; TYPE $6E MY89 L98 ARAP
;
;======================================= =======
LC526 FCB 32 ; COEF RPM/12.5 FILTER
;
LC527 FCB 160 ; 160 STP'S IDLE RPM START UP POSIT, PARK
LC528 FCB 20 ; 20 STP'S ADDED TO WARM PK IF A/C ON
LC529 FCB 5 ; 5 STP'S ADDED FOR FAN ANTICIPATE
LC52A FCB 5 ; 5 STP'S ADDED FOR COLD ENGINE

;--------------------
; REQUESTED RPM
;
;--------------------
LC52B FCB 4 ; 100 RPM/12.5 ADDED IF IN PK/NEUT
LC52C FCB 64 ; 512 msec's, IDLE SPEED START UP DELAY
LC52D FCB 0 ; 0 RPM/12.5, IAC TARGET SPEED OFF SET ADDER

;----------------------------------------------
; IAC TARGET SPEED vs COOLANT TEMP
;
; Dissassemby of ARAP, LINES = 17
;
; TBL = .08 * RPM
;----------------------------------------------
ORG $052E ; RPM Deg c COOL
;----------------------------------
LC52E FCB 84 ; 1050 -40
LC52F FCB 84 ; 1050 -28
LC530 FCB 84 ; 1050 -16
LC531 FCB 84 ; 1050 -4
LC532 FCB 84 ; 1050 8
LC533 FCB 76 ; 950 20
LC534 FCB 72 ; 900 32
LC535 FCB 60 ; 750 44
LC536 FCB 48 ; 600 56
LC537 FCB 48 ; 600 68
LC538 FCB 46 ; 575 80
LC539 FCB 46 ; 575 92
LC53A FCB 46 ; 575 104
LC53B FCB 46 ; 575 116
LC53C FCB 46 ; 575 128
LC53D FCB 46 ; 575 140
LC53E FCB 46 ; 575 152
;----------------------------------------------


;------------------------------
; IAC TARGET SPEED DEADBAND
;------------------------------
LC53F: FCB 6 ; 75 RPM/12.5, MAX ERR FOR PK/NEUT
LC540: FCB 2 ; 25 RPM/12.5, MAX ERR FOR DRIVE
;
LC541: FCB 2 ; 25 RPM/12.5, MAX RPM ERR FOR DEADBAND A/C LEARN & MIN IAC POSIT
LC542 FCB 4 ; 50 RPM/12.5. MAX ERROR FOR DEADBAND FOR MOTER POSIT
;------------------------------


;------------------------------
; PID ENABLE CONDITIONS
;------------------------------
LC543 FCB 3 ; 1%, ENAB T/F IF TPS GT THRESH%
LC544 FCB 0 ; 0, DONT STORE NEW TPS IF ID DIFF VAL < THRESH
LC545 FCB 6 ; 1.8 MPH/3.2, ENAB IAC PID IF Vss > THRESH
LC546 FCB 4 ; 50 RPM/12.5. MIN RPM UNDERSPEED ERR TO ENABLE
; PID DURING TRANSISION DELAY
;----------------------------------------------

;------------------------------
; PORPORTIONAL GAINS,
; (PID)
;------------------------------
LC547 FCB 32 ; 0.01, UNDERSPEED ERROR PROPORTIONAL GAIN, STEPS
LC548 FCB 32 ; 0.01, OVERSPEED ERROR PROPORTIONAL GAIN, STEPS
; arg = VAL * (256 * 12.5)
;
LC549 FCB 255 ; 3187.5 RPM/12.5, MIN RPM UNDERSPEED ERROR TO ENAB
; HI PROPORT GAIN ADDITION, (LC54A)
;
LC54A FCB 0 ; 0, HI PROPORT GAIN ADDITION
; arg = VAL * 256 * 12.5
;----------------------------------------------

;------------------------------
; DERIVITVE GAINS (PID)
; TYPE $6E MY89 L98 ARAP
;------------------------------
LC54B FCB 40 ; 0.010, STEPS, GAIN DERIVITIVE, WHEN RPM RATE IS DECREASEING
LC54C FCB 16 ; 0.004, STEPS, GAIN DERIVITIVE, WHEN RPM RATE IS DECREASEING
; arg = STEPS/(RPM/SEC) * 256 * 15.625


LC54D FCB 22 ; 343.75 RPM/15.625, MIN DECREASING RPM
; RATE TO ENABLE HI GAIN FOR DERIVITIV, RPM/SEC
; arg = RPM/SEC * 15.625
;
LC54E FCB 255 ; 0.064, STEPS, DECREASING RPM RATE HIGH GAIN ADD
; FOR DERIVITIVE. STEPS/(RPM/SEC)
; arg = STEPS/(RPM/SEC) * 256 * 15.625
;
LC54F FCB 4 ; 25/12.5, RPM MIN UNDER SPD ERROR TO ENABLE
; HI PROP & DERIV GAIN ADDITIONS
;----------------------------------------------


;------------------------------
; INTEGRAL GAINS (PID)
; TYPE $6E MY89 L98 ARAP
;------------------------------
LC550 FCB 40 ; 0.00125, STEPS RPM/(RPM-sec),
; PK/NUT INTEGRATOR GAIN IF RPM RATE OUT OF DEADBANDS
; arg = STEPS RPM/(RPM-sec) * 128 * (12.5/0.05)
;
LC551 FCB 40 ; , STEPS RPM/(RPM-sec),
; DRIVE INTEGRATOR GAIN IF RPM RATE OUT OF DEADBANDS
; arg = STEPS RPM/(RPM-sec) * 128 * (12.5/0.05)
;
LC552 FCB 12 ; 187.5 RPM/sec, PK/NUT MAX RPM RATE TO INTEGRATE W/LC550
LC553 FCB 12 ; 187.5 RPM/sec, DRIVE MAX RPM RATE TO INTEGRATE W/LC551
;------------------------------

;------------------------------
; PK/NEUT SCALING GAIN
;------------------------------
LC554 FCB 255 ; 0.996, PK/NEUT MULT FORP PROP & DERIV
; arg = VAL/256



;----------------------------------------------
; THROTTLE FOLLOWER GAINS
; TYPE $6E MY89 L98 ARAP
;
; (msec/6.25)
;----------------------------------------------
LC555 FCB 5 ; 31 msec BETWEEN STP'S IN PK/NEUT
LC556 FCB 4 ; 25 msec BETWEEN STP'S IN DRIVE
; arg = msec/6.25
;
LC557 FCB 7 ; 1326 usec ADD TO TIME BETWEEN FOLLOWER IN DRIVE
; arg = msec * (32/6.25)
;
LC558 FCB 8 ; 50 msec ADD TO TIME BETWEEN FOLLOWER IN OPEN LOOP
; arg = msec/6.25
;
LC559 FCB 192 ; 150 STEPS/%TPS, TPS FOLLOWER SLOPE GAIN
; arg = STEPS/%TPS * 1.28
;
LC55A FCB 75 ; 75, MAX STEPS IN DRIVE
;
LC55B FCB 255 ; 0.996, PK/NEUT STEPS/DRIVE STEPS TF MULT
; arg = VAL * 256
;----------------------------------------------

;----------------------------------------------
; A/C LEARNING GAIN
;----------------------------------------------
LC55C FCB 20 ; 20 STEPS, A/C DEFAULT IF NV MEM FAIL
;
LC55D FCB 32 ; 32 STEPS, MAX A/C LEARN STEPS
LC55E FCB 10 ; 10 STEPS, MIN A/C LEARN STEPS
;
LC55F FCB 5 ; 5 STEPS, MAX PLUS A/C LEARN PWER OFF/ON CYCLE
;
LC560 FCB 20 ; 1000 msec MIN RPM ERR DEAD BAND TIME BEFORE LEARN ENABLE/DISABLE
; arg = msec/50
;
LC561 FCB 128 ; 1, STEPS, P/N NEUT GAIN FOR A/C LEARNED VAL
; (DRIVE STEPS)/(NEUT STEPS) = 1 OVER LC561
; arg = STEPS * 128
;----------------------------------------------



;
; STEPPER MOTOR PARAMS'S
;
LC562 FCB 32 ; 0.125, QUANTIZER GAIN TO CONVERT ALGO OUT FROM LINEAR
; MOTOR GAINS TO STEPS
; cal = GAIN * 256
;
LC563 FCB 8 ; 8, IDLE SPD INVERSE QUANT GAIN TO MAKE
; FRACTIONAL STEPS
;======================================= =======

 

I would check to see what your gas regulator is set at ?

It sounds like its running rich for some reason , do you get any back farting when the idle is low ?

 

Thanx, CFI...Here is the strange part...If I diconnect the est, when I try and set the min. air, I can now get the idle to 700, and have the idle rather steady. I then reset the TPS to .54, and reconnect the IAC. Once I restart the car, the idle goes to about 1300, then drops to the 1050, but no further...The iac position shows in datamaster to be zero, and the counts are about 30, and I can see the IAC counts change, so I am assuming that the IAC is operating properly. The idle stays at 1050, unless I unplug the est, at which time the idle drops to the 700...I would guess that it involves the esc system, but my bet is on something going on between the ECM, or the parameters in the Bin file. I've had the chip for a time, and have not had any problems with it, until this problem appeared...And as you say, I'm still looking for possible air sources, other than the MAF intake....Thanx, I appreciate your input..

Cheers,
Michael

 

Golfman, my fuel pressure is a steady 38#...I don't see any movement in the pressure, unless I open the throttle rapidly...car revs great, and run really well, with no pop in either the intake or exhaust....just got this weird idle problem...

Cheers,
Michael

 

Tequilaboy, Thanx for posting this...checked my bin, and all appears to be correct...I'll be sending you a *.uni file in the next couple of days, maybe you can spot something I'm missing...this just doesn't make any sense to me....Thanx for your assistance...

Cheers,
Michael

 

You should be able to set the minimum air at 400, 450, 500 RPMs. 700 is too high. Something, still is not right.



Does, "iac position shows in datamaster to be zero" mean the IAC is closed? What does "counts are about 30" mean? It doesn't sound like it means the IAC is closed. Please excuse me, I don't speak computer. I have a pretty good idea what is does, but I can't read tables, charts or whatever tequilaboy posted.

It is getting air from somewhere. Could some of that programming be adding more than one value, and actually asking for a 1050 idle? Could there be similar mess up in the timing tables calling excess advance? Do you still have the original chip you can sub in for comparison? Even programming problems don't explain how you can reduce the air (via the min. air adj, screw) yet maintain a 1050 idle.

What did you do most recently before this problem popped up?

RACE ON!!!

 

Is the base timing correct ??

 

Originally Posted by mk842766
I then reset the TPS to .54, and reconnect the IAC. Once I restart the car, the idle goes to about 1300, then drops to the 1050, but no further...The iac position shows in datamaster to be zero, and the counts are about 30, and I can see the IAC counts change, so I am assuming that the IAC is operating properly.

If the IAC position is at zero, and the rpm is still up at 1050 rpm then it getting too much air through the throttle.

Here's what I'm reading into this:

Your min air setting is now effectively 1050 rpm with the EST connected. It is running near 40 degrees of spark advance with the ARAP bin at this rpm. A stock 85 bin for comparison would only be running at 28 degrees of advance at 1000 rpm and light to moderate load.

Now if you close the throttle by turning out on the stop screw, and also making sure that the throttle actually closes more, the idle must come down, unless the IAC begins to open to compensate (which it should not, since the programmed desired idle rpm is much lower than the current rpm). The IAC should still be trying to close until the rpm drops below the target.

Due to the big swings in the ARAP spark table, it may not actually run with any stability as the airflow and rpm is decreased.

Do you still have the 85 iron heads? If so, I think the spark table will need to be adjusted to suit the iron heads. This is starting to stand out as a big difference between ARAP and a stock 85 bin.

If you want, I could send you an 86 iron headed bin to try in your 165 ecm. I know an 85 bin is out of the question.

 

CFI...with the est disconnected, I can indeed get the idle to 450, 500...I just choose to set the idle at 700...here in Houston, the air is so Hot and Heavy, the 500 idle seems just a little low, with the fans coming on so much, and the A/C running almost 12 months of the year...I just feel more comfortable with the idle at 700....About the IAC...as I understand (and I'm a little new to this), the zero indicates that the minimum position is "closed", and the counts indicate how the IAC is moving...most folks into programming seem to indicate they have, or want 20 counts or less.....I've never had a count that low....I agree on it getting air, I just haven't been able to find anywhere it is coming from...I've inspected all around the runners, the injectors,the intake, the MAF, and the ducting, and can find no place where extra air is getting in. I'll be working with Tequilaboy, who has graciously offered to look at my programming, on the chip thing you mentioned...Car ran really well, until this idle thing popped up. Still runs well, except for the idle...nothing was touched, or changed, when this popped up, and other than trying to set the min. air, nothing has changed on the car. Thanx for your insights, they are most appreciated....


Cheers,
Michael

 

Agent 86, I've checked the base timing, several times in the last few days, to verify it is correct....6 Degrees every time...

Cheers,
Michael

 

Tequilaboy...sent you a PM

Cheers,
Michael

 

Set the min idle to 450-500 using the correct procedure. After it is set and TPS is re-set, the ECM will use the idle numbers burned onto the chip, and it won't be 450-500.

 

Yep, tried that several times...always comes back to 1050....that's what is driving me nuts!!!

Cheers,
Michael

 

I just mentioned that because in your previous post, you said you set the min to 700.

 

One thing this post makes me think that you don't understand. When you have the IAC fully closed and disconnected, you are adjusting the "minimum air" adjustment. NOT the idle speed. The idle speed is burned into the chip. The minimum air adjustment IS NOT the idle speed it's sort of like the base timing. Neither, is what the engine will ever run at, but they are a starting place, a reference point for the ECM. Hot and Heavy Houston air is no reason to alter the minimum air adjustment. Unless you set the minimum air faster than the programmed idle speed, the engine will idle at the programmed speed if it within a range that the IAC can achieve. If you want or need a different idle speed, you should have the chip altered. Maybe knowing this will help with the problem.



I think "counts" are the same a steps, the number of "notches" the stepper motor has taken from the closed position. Feel free, anyone, to correct me if I am wrong. Therefore I think the statements, "iac position shows in datamaster to be zero" and "counts are about 30" are contradictory.



Something has triggered this problem. I was hoping thinking about it might light a light bulb. That is why I asked. This MAY be a software and not a hardware problem. Good luck.

RACE ON!!!

 

CFI...I think I might have been a little generous in what I wrote, without making sure I was speaking in literal terms, that make a consistient groundwork for us to understand one another...you are indeed correct, that the min air procedure is just that...setting the min air, as a reference for the ECM...in doing that, I am aware of the implications involved in the process, and understand the relationship with the TPS setting (which I would also classify as a "Reference"). As far as setting the min air at something other than 450...I have not had any success at getting the car to accept an idle that low without dieing before it got to 450, since I have lived in Houston. When I lived in Denver, or Salt Lake City, I was able to get the car to idle that low, but without any air moving here in Houston, no success (and that might be entirely a problem with my vehicle...) I have chosen to set my min air reference point at 700, with the knowledge that the idle speed in my chip is set to 850...still above the min air setting....I apologize if I had not made that clear before.

The datamaster manual describes the IAC Position as: "This is the actual counts (0 to 255) for the Idle Air Control Valve position. This valve controls the idle speed and air density during throttle overrun conditions."

Therefore, I, like you are somewhat confused as to exactly the two terms actually mean. I never really paid that much attention to the two numbers, other than to make sure the IAC Counts number was moving, in the assumption that this meant that the IAC was actually doing something...sorry for confusing the issue here..

I really appreciate your input, and you do indeed cause people to stop and think about things, rather than blindly replacing components, hoping they will fix the problem. You have taught me to slow down, and look at things more closely, look at the FSM, and try and deduce what is REALLY going on, rather than what I THINK is going on. In this case, I have not ruled out ANY possibility, although, like you, I am beginning to suspect a software problem, rather than a hardware problem. Tequilaboy has made a couple of suggestions in his PM for me to look at in the software, but I am continuing to look at the hardware also, before I rule anything out. Thanks for keeping me honest, and for pointing out that I say what I mean, rather than talking in generalities. It's hard have people try and help you, when you talk in generalities.

Thanks again for your input, and I'll keep thinkin'

Cheers,
Michael

 

This might be worth a try. Adjust the min idle till it stalls, then re-set the TPS and see if it helps keep the idle down.

 

Agent 86, you must have read my mind, because that was exactly what I was set to do this evening, when I got home...I guess great minds DO think alike...

Cheers,
Michael

 

I had an identical problem with a Ford a while back. *shudder*

After trying much of what is listed above, we disconnected EVERY connector and cleaned them & recrimped when possible. It went away. Problem never came back.

I don't know what we actually accomplished, but I do know that a glitchy connector can show continuity on a test, but fail to conduct to the sensor/operator.

 

That does have to be an idiosyncrasy of your car. Salt Lake City is at 4200-4500 feet above sea level. Denver is over 5000 feet. In Houston, at sea level, with a barometer of 29.92 in.Hg. as normal, you have 14.7 psi of air pressure forcing air through the gap of your almost closed throttle blades. Up here, our barometer never gets as high as 26", Denver is worse. Setting the minimum air adjustment should be easier in all that luxuriously thick, dense, air.

I really appreciate the first half of your last paragraph. I consider that a very great complement, and I appreciate it. I get PMs from time to time with support and thanks. With all the bashing that goes on, around here in the threads, publicly, it is nice to know that some people "get" me. Thanks again.

I'm not sure that I'll have anything of substance to add to this thread, but I'll keep track. Let us know what the solution is. In the meantime, if I have an epiphany, I'll jump back in. Good luck, and...

RACE ON!!!