I tried searching thru the archives but did not come up w/ anything directly related to my problem so here goes.

The car is an 86 Vette - 165ECM w/ 6E (stock-ish APYP) - SR383 - LPE219 Cam - Manual tranny. IOW not stock.

The problem is that when coming to a stop (clutch pressed) the car wants to "idle" at 1400RPM or so until I come to a complete stop then it drops to 750 - 800 (like the chip says).

What are the likely causes of this? I know there is no magic solution but could someone point me to the right places so I can experiment a bit. Where do I start?

Thanks

Dale

 

Search for "throttle follower"

should net u some decent info
later
JEremy

 

1400 is a bit high. 1100-1200 is a bit more normal for $6E while the car is idling to a stop. I'm not entirely sure this is a throttle follower issue, as the throttle in this condition is closed completely.

I have a strange issue that is slightly similar:

When I start the car the first time, it may eventually settle on the appropriate idle for the given temp, but once I move the first time and come to a stop (the first time), the idle sits a 1500 RPM (or about 60 IAC steps) until stopped for about 5 seconds. Once that happens, the idle settles where it should, and settles immediately on all subsequent stops. Its very strange! This is only seen for the first stop of the drive.

M

 

Throttle follower is an IAC count added at a given throttle opening. Then when the throttle is lifted, the IAC count decays out so that there isn't a huge HC spike. YMMV, zillions of variants.

Then some codes do a IAC reset at a first given MPH and then that decays back out, under different circumstances, again varing by code.

 

None of the $6E hacs I have (APYP, ARAP) have information on IAC vs MPH.

 

I read quite few of the posts that came up searching for "throttle follower" but none of them mention this being implemented in the 6E code. Also There is nothing in the ECU file referring to this (unless it it called something else). Is it only found thru the hack? If so where can I find a copy?

Also it seams that having too much timing at low LV8 in this RPM band (1000-1300) could also cause this. Any thoughts?

Looking at the logs, this is happening with an LV8 of mid-30 to low-40 at 12-1300 RPM with about 28* advance rel to TDC. Would it seem likely that this should be lowered a few deg?

My BLMs are also all over the place (pegged high and low) - probably because some schmoo removed the screens and the fins from inside the MAF.

Hmm... After typing all of this, maybe I should concentrate on the MAF tables first before worrying about the timing?

Any help would be appreciated.

Thanks

 

Magnus,

My 8D, '7730 305 '90 Camaro does the exact same thing. I've messed with untold parameters for two years now with no change in this behavior. It is quite annoying. My kingdom for an answer! :-)

Regards,
Gary Anderson

 

You've been thru these, and read RBob IAC document?.
All this really should cover it.

;--------------------------------------------------
; IAC MANUAL Throttle Follower vs MPH
; TBL = MPH/12.5
;--------------------------------------------------
; STEPS MPH
;----------------------------------
L86B2:
FCB 0 ; 0 0
FCB 4 ; 50 4
FCB 8 ; 100 8
FCB 12 ; 150 12
FCB 12 ; 150 16
FCB 12 ; 150 20
FCB 12 ; 150 24
FCB 12 ; 150 28
FCB 12 ; 150 32
FCB 12 ; 150 36
FCB 12 ; 150 40
FCB 12 ; 150 44
FCB 12 ; 150 48
FCB 12 ; 150 52
FCB 12 ; 150 56
FCB 12 ; 150 60
FCB 12 ; 150 64

;--------------------------------------------------
; IDLE SPEED TIME OUT IAC STEPS vs COOLANT or MAT
; TBL = STEPS
;--------------------------------------------------
; STEPS Deg c
;----------------------------------
L86A1:
FCB 30 ; 30 -40
FCB 30 ; 30 -28
FCB 30 ; 30 -16
FCB 30 ; 30 -4
FCB 30 ; 30 8
FCB 30 ; 30 20
FCB 30 ; 30 32
FCB 40 ; 40 44
FCB 40 ; 40 56
FCB 45 ; 45 68
FCB 50 ; 50 80
FCB 60 ; 60 92
FCB 60 ; 60 104
FCB 60 ; 60 116
FCB 60 ; 60 128
FCB 60 ; 60 140
FCB 60 ; 60 152

L86A0: FCB 50 ; SEC TO LEARN MIN MOTOR KA STEPS
L8699: FCB 40 ; DEFAULT KEEP ALIVE MOTOR STEPS
L866A: FCB 160 ; MAX STEP MOTOR POSIT POSSIBLE WORST CASE VALUE, \(from orifice\)
L8629: FCB 160 ; 160 STP'S IDLE RPM START UP POSIT, PARK

 

Grumpy,

Throttle follower vs MPH, I have 0 steps from 30 MPH down.

Time out steps vs coolant I thought was part of the start up IAC routine, I have 10 steps from 56*C up.

L8699 I have set to 20 steps, this is also used for IAC start up routine, correct?

L86AO, sec. to learn min motor ka steps, I assume converts to msecs and I really don't know what it does.

Any clues?

Regards,
Gary Anderson

 

Question: Does this apply to the $6E? Is there anything in the hack?

Question: Where can I get a copy of the hack? Reading that should answer some of my other questions.

Thanks

Dale

 

Can either of you (Dale, Gary) post a short section of a data log? Say from a 15 MPH rolldown to a stop. At a minimum needs to include MPH, RPM, IAC, SA, PW, & TPS. Other parameters are welcome (O2, MAP, INT, BLM. . . ).

RBob.

 

A little unrelated, but my TBI car does the same thing.

i cut the MAX TF Steps down to 10, that helped the issue, but it is still a bit higher (read: 800-900 RPM commanded idle at 650) until i come to a complete stop. I should try setting it to Zero, and see how it behaves then.

as RBob likes to say...

"The IAC rears its ugly head again...."

 

Here is a CSV file in ZIP format for a short run. The clutch is pressed for the entire file and the car doesn't drop to "idle" until the very end.

Here is a csv file suitable for excel or similar: http://www.1986corvette.info/csv


Record # TimeStamp Cool Temp RPM Speed IAC Pos Spark Adv Inj BPW TPS Volts O2 Volts LTerm-P LTerm-C Load Var STerm-C STerm-P Fuel Trim Cell
Units--> mS ?C RPM MPH Counts Degrees mS Volts mV Percent Counts Counts Counts Percent Number
1 0 74 1200 12 32 26.7 1.71 0.59 670 9.4 140 42 128 0 2
2 247 74 1175 12 32 26.4 1.74 0.59 426 9.4 140 44 128 0 2
3 452 74 1175 12 32 26.7 1.68 0.59 555 9.4 140 43 128 0 2
4 653 74 1150 12 32 25.7 1.74 0.59 852 9.4 140 44 128 0 2
5 857 74 1150 12 32 25.7 1.74 0.59 488 9.4 140 44 127 -0.8 2
6 1049 74 1175 12 32 26 1.74 0.59 400 9.4 140 44 127 -0.8 2
7 1244 74 1150 12 32 25.7 1.79 0.59 351 9.4 140 45 127 -0.8 2
8 1448 74 1150 11 32 25.7 1.77 0.59 324 9.4 140 44 128 0 2
9 1664 74 1200 11 32 26.7 1.77 0.59 329 9.4 140 43 131 2.3 2
10 1889 74 1200 11 32 26.7 1.79 0.59 337 9.4 140 43 132 3.1 2
11 2087 74 1200 11 32 28.1 1.68 0.59 821 9.4 140 42 132 3.1 2
12 2289 74 1200 11 32 28.1 1.68 0.59 844 9.4 140 42 131 2.3 2
13 2479 74 1200 11 32 26.7 1.74 0.59 626 9.4 140 42 131 2.3 2
14 2680 74 1200 11 32 26.7 1.75 0.59 364 9.4 140 43 131 2.3 2
15 2883 74 1200 11 32 27.1 1.69 0.59 444 9.4 140 43 131 2.3 2
16 3078 74 1175 10 32 26.7 1.75 0.59 400 9.4 140 43 131 2.3 2
17 3271 74 1175 10 32 27.1 1.74 0.59 622 9.4 140 43 131 2.3 2
18 3464 74 1200 10 32 27.4 1.74 0.59 613 9.4 140 42 131 2.3 2
19 3666 74 1225 10 32 27.4 1.68 0.59 857 9.4 140 42 130 1.6 2
20 3861 74 1200 10 32 27.1 1.72 0.59 511 9.4 140 43 129 0.8 2
21 4058 74 1225 10 32 27.4 1.71 0.59 462 9.4 140 42 129 0.8 2
22 4261 74 1200 10 32 27.1 1.68 0.59 848 9.4 140 42 129 0.8 2
23 4460 74 1175 10 32 26.4 1.74 0.59 537 9.4 140 43 129 0.8 2
24 4658 74 1175 10 32 26 1.75 0.59 417 9.4 140 44 129 0.8 2
25 4862 74 1200 9 32 26.7 1.74 0.59 417 9.4 140 43 129 0.8 2
26 5063 74 1175 9 32 26.4 1.75 0.59 626 9.4 140 44 129 0.8 2
27 5268 74 1175 9 32 26 1.75 0.59 511 9.4 140 44 129 0.8 2
28 5460 74 1175 9 32 26 1.75 0.59 666 9.4 140 44 129 0.8 2
29 5648 74 1175 9 32 26.7 1.71 0.59 870 9.4 140 43 129 0.8 2
30 5850 74 1200 9 32 26.4 1.68 0.59 888 9.4 140 43 127 -0.8 2
31 6046 74 1175 9 32 26 1.72 0.59 586 9.4 140 44 127 -0.8 2
32 6245 74 1175 9 32 26.4 1.71 0.59 360 9.4 140 43 127 -0.8 2
33 6449 74 1150 9 32 25.7 1.74 0.59 346 9.4 140 44 128 0 2
34 6651 74 1175 9 32 26.7 1.72 0.59 369 9.4 140 43 129 0.8 2
35 6865 74 1200 8 32 26.7 1.74 0.59 462 9.4 140 43 130 1.6 2
36 7068 74 1175 8 32 27.1 1.66 0.59 737 9.4 140 43 130 1.6 2
37 7268 74 1175 8 32 25.7 1.69 0.59 848 9.4 140 43 130 1.6 2
38 7464 74 1175 8 32 26.7 1.69 0.59 759 9.4 140 43 130 1.6 2
39 7656 74 1200 8 32 27.1 1.66 0.59 435 9.4 140 43 130 1.6 2
40 7854 74 1200 8 32 26.7 1.69 0.59 857 9.4 140 43 130 1.6 2
41 8053 74 1200 8 32 27.1 1.72 0.59 417 9.4 140 43 130 1.6 2
42 8250 74 1200 8 32 26.7 1.66 0.59 781 9.4 140 43 130 1.6 2
43 8443 74.8 1175 8 32 26.7 1.75 0.59 639 9.4 140 43 130 1.6 2
44 8644 74 1175 7 32 26.7 1.69 0.59 852 9.4 140 42 129 0.8 2
45 8853 74 1175 7 32 26.7 1.68 0.59 519 9.4 140 43 129 0.8 2
46 9056 74 1175 7 32 26.7 1.68 0.59 480 9.4 140 43 129 0.8 2
47 9246 74 1175 7 32 25.7 1.75 0.59 373 9.4 140 43 129 0.8 2
48 9442 74 1175 7 32 26.4 1.75 0.59 342 9.4 140 43 129 0.8 2
49 9634 74 1175 7 32 26.4 1.72 0.59 813 9.4 140 43 130 1.6 2
50 9830 74.8 1175 7 32 26 1.74 0.59 866 9.4 140 43 130 1.6 2
51 10035 74.8 1175 7 32 26.4 1.69 0.59 875 9.4 140 43 128 0 2
52 10236 74.8 1150 7 32 25 1.79 0.59 861 9.4 140 44 128 0 2
53 10436 74.8 1150 7 32 25.7 1.71 0.59 746 9.4 140 45 127 -0.8 2
54 10637 74.8 1150 6 32 25.7 1.69 0.59 866 9.4 140 44 127 -0.8 2
55 10837 74.8 1150 6 32 25.7 1.69 0.59 879 9.4 140 44 127 -0.8 2
56 11028 74.8 1150 6 32 25.7 1.71 0.59 435 9.4 140 43 126 -1.6 2
57 11231 74.8 1175 6 32 25.7 1.69 0.59 360 9.4 140 44 126 -1.6 2
58 11433 74.8 1175 6 32 26.7 1.69 0.59 320 9.4 140 43 127 -0.8 2
59 11631 74.8 1175 6 32 26.7 1.72 0.59 306 9.4 140 43 129 0.8 2
60 11824 74.8 1200 6 32 26.7 1.75 0.59 293 9.4 140 42 131 2.3 2
61 12030 74.8 1200 6 32 28.1 1.75 0.59 302 9.4 140 42 133 3.9 2
62 12225 74.8 1225 6 32 28.1 1.69 0.59 813 9.4 140 41 134 4.7 2
63 12427 74.8 1225 6 32 28.5 1.69 0.59 875 9.4 140 42 134 4.7 2
64 12625 74.8 1225 6 32 28.1 1.68 0.59 884 9.4 140 42 132 3.1 2
65 12824 74.8 1200 6 32 27.4 1.66 0.59 892 9.4 140 43 130 1.6 2
66 13032 74.8 1175 5 32 26.4 1.66 0.59 897 9.4 140 43 128 0 2
67 13233 74.8 1175 5 32 26.4 1.65 0.59 892 9.4 140 44 126 -1.6 2
68 13437 74.8 1150 5 32 25.3 1.68 0.59 852 9.4 140 45 124 -3.1 2
69 13637 74.8 1100 5 32 24.6 1.77 0.59 444 9.4 140 46 122 -4.7 2
70 13837 74.8 1100 5 32 24.6 1.74 0.59 355 6.3 136 47 122 -4.7 1
71 14040 74.8 1100 5 32 24.3 1.75 0.59 351 6.3 136 46 123 -3.9 1
72 14241 74.8 1075 5 32 24.3 1.69 0.59 648 6.3 136 47 123 -3.9 1
73 14441 74.8 1100 5 32 24.6 1.72 0.59 373 6.3 136 46 123 -3.9 1
74 14648 74.8 1075 5 32 23.6 1.79 0.59 306 6.3 136 47 124 -3.1 1
75 14850 74.8 1075 5 32 23.9 1.8 0.59 284 6.3 136 47 126 -1.6 1
76 15055 74.8 1100 5 32 24.6 1.77 0.59 271 6.3 136 46 128 0 1
77 15255 74.8 1125 5 32 25 1.8 0.59 293 6.3 136 46 130 1.6 1
78 15454 74.8 1150 5 32 25.3 1.77 0.59 337 6.3 136 43 132 3.1 1
79 15659 74.8 1175 5 32 26.7 1.72 0.59 599 6.3 136 42 133 3.9 1
80 15860 74.8 1200 5 32 26.7 1.72 0.59 693 6.3 136 42 133 3.9 1
81 16060 74.8 1200 4 32 27.1 1.72 0.59 329 6.3 136 42 133 3.9 1
82 16256 74.8 1225 4 32 26.7 1.74 0.59 342 6.3 136 41 135 5.5 1
83 16464 74.8 1225 4 32 27.4 1.77 0.59 626 6.3 136 41 135 5.5 1
84 16666 74.8 1225 4 32 28.1 1.75 0.59 684 7.8 138 42 135 5.5 1
85 16872 74.8 1225 4 32 27.4 1.71 0.59 852 7.8 138 41 135 5.5 1
86 17077 74.8 1225 4 32 27.4 1.69 0.59 879 7.8 138 41 133 3.9 1
87 17278 74.8 1225 4 32 28.1 1.65 0.59 835 7.8 138 42 131 2.3 1
88 17482 74.8 1200 4 32 27.4 1.65 0.59 533 7.8 138 43 131 2.3 1
89 17683 74.8 1175 4 32 26 1.68 0.59 466 7.8 138 44 131 2.3 1
90 17891 74.8 1175 4 32 26.7 1.68 0.59 568 7.8 138 43 131 2.3 1
91 18089 74.8 1175 4 32 26.7 1.66 0.59 879 7.8 138 43 131 2.3 1
92 18282 74.8 1200 4 32 26.7 1.68 0.59 875 7.8 138 43 129 0.8 1
93 18482 74.8 1175 4 32 26.4 1.72 0.59 582 7.8 138 43 128 0 1
94 18678 74.8 1175 4 32 26.4 1.71 0.59 551 7.8 138 43 128 0 1
95 18873 74.8 1175 4 32 26.7 1.72 0.59 408 7.8 138 44 128 0 1
96 19079 74.8 1200 4 32 26.7 1.71 0.59 480 7.8 138 43 128 0 1
97 19280 74.8 1175 4 32 26.7 1.71 0.59 528 7.8 138 43 128 0 1
98 19476 74.8 1175 4 32 26 1.72 0.59 426 7.8 138 44 128 0 1
99 19680 74.8 1175 4 32 25.7 1.72 0.59 346 7.8 138 43 129 0.8 1
100 19880 74.8 1150 4 32 25.7 1.79 0.59 382 7.8 138 44 129 0.8 1
101 20172 74.8 1200 4 32 27.1 1.65 0.59 821 7.8 138 42 131 2.3 1
102 20385 74.8 1175 4 32 25.7 1.72 0.59 875 7.8 138 43 131 2.3 1
103 20589 74.8 1175 4 32 26.4 1.74 0.59 395 7.8 138 43 130 1.6 1
104 20789 74.8 1200 4 32 26.7 1.71 0.59 519 7.8 138 42 130 1.6 1
105 20997 74.8 1200 4 32 26.7 1.71 0.59 537 7.8 138 43 130 1.6 1
106 21198 74.8 1175 4 32 26.4 1.68 0.59 777 7.8 138 43 130 1.6 1
107 21395 74.8 1175 3 32 26.4 1.75 0.59 582 7.8 138 43 130 1.6 1
108 21591 74.8 1200 3 32 26.7 1.71 0.59 448 7.8 138 43 130 1.6 1
109 21790 74.8 1200 3 32 26.7 1.63 0.59 839 7.8 138 43 130 1.6 1
110 21986 74.8 1200 3 32 26.7 1.66 0.59 866 7.8 138 43 130 1.6 1
111 22182 74.8 1175 3 32 26.7 1.65 0.59 737 7.8 138 43 129 0.8 1
112 22390 74.8 1175 3 32 26 1.68 0.59 764 7.8 138 44 129 0.8 1
113 22595 74.8 1150 3 32 26 1.75 0.59 506 7.8 138 44 129 0.8 1
114 22792 74.8 1125 3 32 25.7 1.72 0.59 630 7.8 138 44 129 0.8 1
115 22995 74.8 1150 3 32 25.7 1.72 0.59 426 7.8 138 45 129 0.8 1
116 23196 74.8 1150 3 32 26 1.69 0.59 702 7.8 138 44 129 0.8 1
117 23398 74.8 1150 3 32 26.4 1.65 0.59 746 7.8 138 43 129 0.8 1
118 23599 74.8 1175 3 32 26.4 1.65 0.59 848 7.8 138 43 128 0 1
119 23797 74.8 1150 3 32 25.7 1.75 0.59 475 7.8 138 44 128 0 1
120 24006 74.8 1150 3 32 25.7 1.74 0.59 346 7.8 138 44 128 0 1
121 24203 74.8 1150 3 32 26.7 1.75 0.59 408 7.8 138 44 129 0.8 1
122 24410 74.8 1150 3 32 25.7 1.77 0.59 440 7.8 138 44 129 0.8 1
123 24609 74.8 1175 3 32 26.7 1.75 0.59 453 7.8 138 44 129 0.8 1
124 24808 74.8 1175 3 32 26 1.75 0.59 386 7.8 138 44 129 0.8 1
125 25006 74.8 1175 3 32 26 1.74 0.59 471 7.8 138 44 129 0.8 1
126 25203 74.8 1175 3 32 26.4 1.72 0.59 444 7.8 138 43 129 0.8 1
127 25402 74.8 1150 3 32 26 1.74 0.59 844 7.8 138 44 130 1.6 1
128 25609 74.8 1150 3 32 26 1.74 0.59 866 7.8 138 44 129 0.8 1
129 25803 74.8 1125 2 30 25.3 1.74 0.59 670 7.8 138 45 129 0.8 1
130 26022 74.8 1150 2 23 25 1.68 0.59 360 7.8 138 42 129 0.8 1
131 26239 74.8 1125 2 18 24.3 1.63 0.59 386 7.8 138 41 130 1.6 1
132 26465 74.8 1075 2 18 22.5 1.66 0.59 493 7.8 138 43 130 1.6 1
133 26684 74.8 1000 2 18 21.1 1.86 0.59 360 7.8 138 47 131 2.3 1
134 26892 74.8 925 0 18 21.8 1.97 0.59 329 7.8 138 50 131 2.3 1
135 27098 74.8 925 0 18 21.8 2 0.59 857 7.8 138 49 131 2.3 1
136 27305 74.8 925 0 18 20.7 1.91 0.59 901 7.8 138 48 131 2.3 1
137 27508 74.8 950 0 17 20.7 1.94 0.59 910 7.8 138 48 131 2.3 1
138 27725 74.8 950 0 17 20.7 1.85 0.59 915 7.8 138 48 131 2.3 1
139 27941 74.8 950 0 16 20.4 1.85 0.59 906 7.8 138 47 131 2.3 1
140 28152 74.8 925 0 15 20.7 1.91 0.59 897 7.8 138 48 131 2.3 1
141 28373 74.8 950 0 15 20.7 1.86 0.59 706 7.8 138 47 131 2.3 1
142 28588 74.8 925 0 15 20.4 1.89 0.59 879 7.8 138 48 131 2.3 1
143 28792 74.8 900 0 15 21.1 2 0.59 848 7.8 138 49 131 2.3 1
144 29004 74.8 925 0 14 20.4 1.88 0.59 879 7.8 138 48 131 2.3 1
145 29220 74.8 950 0 14 20.4 1.82 0.59 879 7.8 138 46 131 2.3 1
146 29426 74.8 925 0 14 20.4 1.92 0.59 542 7.8 138 47 131 2.3 1
147 29634 74.8 925 0 14 20.7 1.88 0.59 408 7.8 138 46 131 2.3 1
148 29838 74.8 950 0 14 20.4 1.83 0.59 613 7.8 138 46 131 2.3 1
149 30041 74.8 925 0 14 20.4 1.83 0.59 875 7.8 138 46 131 2.3 1
150 30248 74.8 925 0 13 20.4 1.89 0.59 577 7.8 138 47 131 2.3 1
151 30463 75.5 950 0 12 20.4 1.89 0.59 448 7.8 138 47 131 2.3 1

 

Check the TF steps value at $540. It is the minimum TF steps setting for when the vehicle speed is above the MPH value at $53E.

This will cause the IAC to be held open a little until the vehicle speed drops below that MPH setting.

RBob.

 

Looking at the log the IAC is staying open at 32 steps until the vehicle speed drops below 3 MPH. The IAC then goes to 12 steps.

I need to check some items later today. I think that like the '8746 there is a minimum TF steps count.

RBob.

 

so i have one of two options here then.

raise the value $53E or drop the value in $540, correct?

does the min TF override the max TF steps value (sorry, I am at work, I don't have the address to refrence.)

 

86Chicken, couple of things to try. There is a minimum TF steps count ($6E code) at $57A. Can reduce that value.

I looks like another problem may be that learning is not taking place. The data log coolant temperature is at 74°C which is below the 85°C threshold in APYP.

This term is at $598. The math being the common °C = (bin * .75) - 40.

If the A/C request signal is incorrect that can also cause problems (IE: no A/C yet the ECM is being told the A/C is on). Same with fans. The IAC gets kicked up whenever the A/C or a cooling fan is on. That stuff needs to be correct also.

HTH,

RBob.

 

The MPH value in $53E also affects which TF decay coeficient is used.

Don't know which overrides which.

RBob.

 

86 -

I've just added the items RBob mentions to the 6Ev011.ecu file available here:

http://www.supportfitness.com/mark/t...cus/6Ev011.ecu

You'll notice them under the IAC params in the constants list, specifically:

IAC Steps added to T/F in Drive
Enable IAC PID if MPH is GT
IAC Default Keep Alive Motor Steps

I did not increment the version number of the file because I am going to continue improving the ECU for the 4.0 release.

M

 

Cool - I'll give this a try in the morning and report back with the results. Sounds like this might be the ticket to getting this car drivable.

Could someone point me to the location of the hack for $6E? I know where the $8d is for my 90 Vette but I would like to study up on the 86 code.

Thanks for all the help!!

Dale

 

www.moates.net

click on the file manager in the left side nav menu.

 

RBob-

I'll get a log but can't get to it until the weekend. What exactly does "enable IAC pid if VSS > x MPH" (located at L8649 in the 8D) do? My stock bin is set at .9 MPH.

How about at LB906 there is a mention of "warm kickdown" but that is the only place it is mentioned. Is this an instance of a code fragment that never was used?

Regards,
Gary Anderson

 

Thanks for the link. Should prove to be some good info.

I fiddled with the "IAC Steps added to T/F in drive" and it appears to keep the IAC in check.

It was set at 10. I moved it to 5 and the idle would drop like a rock to the desired speed (800) making for some pretty aggressive engine braking. Unfortunately this car has a really touchy throttle and this makes it real strange to drive. I put it back to 7 and it would not drop past 1100 RPM so I think 6 is the magic number for this car.

I am currently massaging the 6E timing to get closer to the LPE timing (where the car ran OK) which has much less advance and should also improve the idle characteristics quite a bit.

I think we can write this problem off as solved (for me anyway).

Thanks for the help!!!

Dale

 

RBob,

Here is a short data log of a neutral coast down.
MPH,RPM, IAC,TPS%, MAP
31, 1900, 42, 7.8, 34.7
31, 1900, 42, 7.8, 34.7
31, 1925, 42, 7.1, 34.3
31, 1900, 42, 7.1, 33.2
31, 1925, 42, 6.3, 32.9
31, 1900, 42, 6.3, 33.2
31, 1925, 42, 7.1, 32.9
31, 1900, 42, 7.1, 32.9
31, 1850, 42, 6.3, 32.9
31, 1875, 42, 6.3, 32.9
31, 1900, 42, 6.3, 32.9
31, 1900, 42, 6.3, 32.9
31, 1900, 42, 6.3, 33.2
31, 1900, 42, 6.3, 32.9
31, 1900, 42, 6.3, 33.2
31, 1900, 42, 6.3, 33.2
31, 1875, 42, 6.3, 32.5
30, 1900, 42, 6.3, 32.1
31, 1875, 42, 5.9, 31.8
30, 1800, 42, 0.0, 24.4
30, 1850, 42, 0.0, 22.2
30, 1800, 42, 0.0, 22.2
30, 1825, 42, 0.0, 22.2
29, 1800, 42, 2.7, 24.0
29, 1775, 42, 3.9, 28.4
29, 1750, 42, 3.9, 30.3
28, 1725, 42, 10.2, 28.8>
28, 1900, 42, 19.2, 74.6> blip throttle to pull into neutral
28, 2250, 42, 0.0, 26.6
28, 1925, 42, 0.0, 22.2
28, 1650, 42, 0.0, 22.9
28, 1375, 42, 0.0, 24.7
27, 1150, 42, 0.0, 27.0
25, 975, 42, 0.0, 31.8
24, 925, 42, 0.0, 35.1
23, 925, 41, 0.0, 36.6
22, 975, 41, 0.0, 35.8
21, 1000, 41, 0.0, 35.1
20, 1000, 41, 0.0, 34.7
19, 1025, 41, 0.0, 34.3
18, 1000, 41, 0.0, 34.0
17, 1000, 40, 0.0, 34.3
16, 1000, 40, 0.0, 34.0
15, 1000, 40, 0.0, 34.3
15, 1000, 40, 0.0, 34.3
14, 975, 40, 0.0, 34.3
13, 975, 40, 0.0, 34.7
12, 975, 40, 0.0, 34.7
12, 975, 40, 0.0, 34.7
11, 1000, 39, 0.0, 34.3
10, 1000, 39, 0.0, 34.0
10, 975, 39, 0.0, 34.3
9, 975, 39, 0.0, 34.0
8, 975, 39, 0.0, 34.3
8, 1000, 39, 0.0, 34.3
8, 975, 39, 0.0, 34.0
7, 975, 38, 0.0, 34.0
7, 975, 38, 0.0, 34.0
6, 975, 38, 0.0, 34.0
6, 975, 38, 0.0, 34.0
6, 975, 37, 0.0, 34.0
5, 975, 37, 0.0, 34.0
4, 975, 37, 0.0, 34.0
4, 975, 37, 0.0, 33.6
4, 975, 37, 0.0, 34.0
3, 975, 37, 0.0, 34.0
3, 975, 37, 0.0, 34.0
3, 975, 37, 0.0, 34.0
3, 975, 37, 0.0, 33.6
2, 950, 37, 0.0, 34.0
2, 975, 37, 0.0, 34.0
2, 950, 37, 0.0, 34.3
2, 975, 37, 0.0, 34.0
2, 975, 37, 0.0, 34.0
2, 975, 37, 0.0, 33.6
2, 975, 37, 0.0, 33.6
0, 975, 37, 0.0, 34.3
0, 1000, 36, 0.0, 33.6
0, 1025, 35, 0.0, 33.2
0, 1000, 33, 0.0, 32.9
0, 975, 31, 0.0, 32.9
0, 950, 30, 0.0, 32.9
0, 925, 29, 0.0, 32.9
0, 900, 29, 0.0, 33.2
0, 875, 28, 0.0, 34.0
0, 900, 28, 0.0, 34.3
0, 900, 28, 0.0, 34.3
0, 900, 27, 0.0, 34.3
0, 875, 27, 0.0, 34.3
0, 900, 27, 0.0, 34.7
0, 875, 26, 0.0, 34.3
0, 900, 26, 0.0, 34.0
0, 900, 26, 0.0, 33.6
0, 875, 26, 0.0, 34.0
0, 875, 25, 0.0, 34.0
0, 850, 25, 0.0, 34.0
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 35.1
0, 875, 25, 0.0, 34.7
0, 875, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.3
0, 875, 25, 0.0, 34.3
0, 850, 25, 0.0, 34.3
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 875, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 850, 25, 0.0, 34.7
0, 825, 25, 0.0, 35.1
0, 850, 25, 0.0, 34.7

Regards,
Gary Anderson

 

Can someone tell me how to change this from a text file to a bin file? I am still very new to this and I can't figure it out. May be I'm making it harder that it is, either way I havn't been able to do it.
Thanks guys

Dewayne

 

right click on the link to it, save as.

 

Thanks Mangus.

 

What coolant temperature is the engine running at?

RBob.

 

That's what I'm thinking is happening. The coolant temp vs IAC step is a table that I had to half in my calibration just to get it to run half decent. It was putting too much load on my rear brakes in the cold. The engine just wanted to keep pulling (also had a tad too much timing) but it was a real PITA.
Anything after 160 deg F I have the coolant influenced step adder set to 10. Below that there is more but nothing like the stock calibration. That last straw was when it snowed and the car just had no traction and I had thought my throttle was stuck!
It's nice for emissions but until I get traction control the IAC is limited to stall saver duty and cold start .

 

Gentlemen,

Coolant temp was 95-100*F during this sequence. If "Idle speed timeout steps vs coolant temp" is the table you are refering to mine is set at 20 steps in this range. I was under the impression this table was used for startup purposes. Is that incorrect? My "max MPH for idle" is set at 10 MPH and the commanded idle speed for that temp is 850 RPM. Is that any help? Thanks.

Regards,
Gary Anderson

 

FWIW, that's way too cold.
If it was just a cold engine, that's one thing, but for a normal operating temp., you'll be chasing around trying to get things right. One often ignored component of the tune is fuel temps., with the heads being that cool the fuel isn't going to pick up much heat, so it'll be more gobule like then in a warmer engine. Not to mention the summer/winter brew changes will have more of an impact on your tune.

And the old stuff about running cooler thermostats is pretty mcuh history. Proper tuned, and design executed, there's no real need for that anymore. Cooler then 180 and your doing more long term harm then good. Talking street cars here.

 

That was on a cold, first start of the day engine. Had about 5-6 minutes running time and 2-3 miles before the coast down sequence. The post by Magnus somewhere above states and my car echoes it "the first time on a newly started motor". After the first stop the idle speed will stabilize and drop as soon as I lift, within reason.

Today, on the ride home from work it wasn't raining for the first time in about two weeks and traffic was almost nonexistant. My commute covers two lane county and state roads with speed limits from 45-55 MPH with several stop signs thrown in for good measure. With the no traffic I made all the stops rolling and with a fully warmed up motor (180*F) and about 18 miles into the ride I made the first complete stop. The IAC hung at @ 25 steps (@1200-1300 RPM) until the complete stop was made and a short delay. (maybe 1-2 seconds) It then dropped to @ 3-5 steps and idled at the requested 775 RPM. Normal IAC position at idle is 0-10 steps depending on weather (temp,humidity, etc.) After this first stop the motor will drop to idle any time you lift and either clutch or shift to neutral.

Regards,
Gary Anderson

 

(see post right above) Sounds like it is working the way it should. As you mentioned location $699 has been changed to 20 steps. I would lower it to 10 steps and see if that changes how the IAC steps down.

Currently it goes to 25 during coast down (before learn). If my guess is correct changing $699 to 10 steps will cause the IAC to go to 15 steps on a coast down.

If so you have it beat.

RBob.

 

Gary - this does indeed describe -exactly- what my car does. Let me know if you find the solution (I'm working on other little tuning gremlins at the moment). I'd love to make this stop happening.

Weird thing is, I really don't remember when this started happening. I know its been doing it for quite a while now (2 years maybe), but I don't remember noting it mentally in the earlier years of my ownership of the vehicle (maybe it started after my engine swap). Its definately code/program related though.

 

RBob,

$699 to 10 steps, will try tomorrow. Do you think $6A0 could be the delay from the time the car stops until the IAC starts to fall? Just checked, I'm thinking not. My bin is set at 00, stock AXCY is 64. We'll see what tomorrow brings. Thanks.

Regards,
Gary Anderson

 

Gary, the value at $6A0 looks to be the amount of time (seconds *10) that an idle speed needs to be held before the keep alive idle steps are saved. IOW a delay before the idle steps are saved as the ones to use.

I too noted how the IAC delayed before dropping the steps down (in your data log). I looked around to see if I could find what causes that but didn't. There are some other delays that it may be one of.

RBob.

 

Sorry to report, no change today. It still has to be a complete stop and then a 1-2 second delay. At that point the IAC drops quite quickly to the commanded idle speed. Engine temp, driving distance, commanded idle speed, none of these seem to make any difference. Todays chip had $699 set at 8 steps and each of the three times i drove the car today the idle would hang @1200-1300 until the first complete stop. After the first stop it will drop to the commanded idle speed almost instantly.

It almost seems to be VSS related. What exactly does "enable IAC pid if VSS > x MPH" (located at L8649 in the 8D) do? My stock bin is set at .9 MPH. Thanks guys.

Regards,
Gary Anderson

 

I know this thread is old news but I have the same issue on my Vette with 1227165 6e. Hangs until the 1st full stop. On subsequent stops it is better but I think still a little slow to decay. Tune started as ARAP a long time ago. Tried everything in this thread and others. Any help?