Can someone point me in the right direction?

I'm trying to tune something that I don't have much experience with. DFCO + idle after a stop. I'm having this issue thats driving me absolutely crazy.. When I slow down to a stop (0% tps) the idle hangs around 1300rpm until I come to a complete stop, then it hangs for a few ms then drops to my set idle (800rpm).

I want it to drop to 800 sooner, even if i'm still moving. I have the max speed for idle set to 14mph.. I have a log of me rolling at 7, 5, then 3mph and the idleing hanging until after I stop.

Is this part of DFCO? Or is there some other routines that effect this?

DFCO RPM enable:1200
DFCO RPM disable: 1000
DFCO MAP enable: 21
DFCO MAP disable: 27

MAX %TPS for idle: 3.1%

Now for log data:
<PRE>
RPM MapV TPSV MPH TPS % MAP kpa IAC
1300 1.47 0.73 5 0 37.71 5
1300 1.45 0.73 5 0 37.35 5
1275 1.47 0.73 5 0 37.71 5
1275 1.47 0.73 5 0 37.71 5
1250 1.51 0.73 5 0 38.42 5
1250 1.49 0.73 5 0 38.07 5
1225 1.51 0.73 3 0 38.42 4
1225 1.51 0.73 3 0 38.42 3
1225 1.53 0.73 3 0 38.78 3
1200 1.57 0.73 3 0 39.5 3
1175 1.61 0.73 3 0 40.21 3
1175 1.63 0.73 3 0 40.57 3
1150 1.67 0.73 3 0 41.28 3
1150 1.71 0.73 3 0 42 3
1125 1.75 0.73 3 0 42.71 3
1150 1.75 0.73 3 0 42.71 3
1125 1.78 0.73 0 0 43.43 1
1100 1.76 0.73 0 0 43.07 0
1100 1.8 0.73 0 0 43.79 0
1075 1.84 0.73 0 0 44.5 0
1050 1.84 0.73 0 0 44.5 0
1025 1.9 0.73 0 0 45.57 0
1000 1.98 0.73 0 0 47 0

..And from here on i'm happy..

975 2 0.73 0 0 47.36 0
950 2.1 0.73 0 0 49.15 0
900 2.2 0.73 0 0 50.93 0
875 2.29 0.73 0 0 52.72 0

</PRE>

I guess when i've gotten myself to the point that I'm picking at things like this I'm "happy" with everything else. Truth is, I am. I think my AFR is just about right everywhere (only some dyno testing now will tell under boost), and drivability is great.

-- Joe

 

no but theres a IAC follwer vs MPH in the code. im not sure where it is but that whats your fighting. it keeps the car from stalling. i rarely ever bother with it.

 

Thats different from max speed vs idle?? .. Perhaps TC doesn't have a table for this routine?

 

The log looks a little odd in that the IAC counts are very low.
But the closed TPS voltage is really high.

I'd check the sensor, and all the idle settings, and may redo things a lil to drop the idle TPS voltage.
By idle settings also timing and AFR.

 

The idle control logic needs to see 0 (zero) MPH before it will bring an idle speed down (it can still be brought up).

'730 & $8D IIRC? Check the SA in the closed throttle SA table in the 1200-1400 RPM area. May need to lower it. As Bruce mentioned the tune in this area may be that it runs too good at 1200 RPM and doesn't want to come down to idle.

As a side note on a port injected setup it isn't as important to idle with low (or 0) IAC counts vs a TBI setup.

RBob.

 

My '730 '90 305 TPI Camaro does the exact same thing. Idle TPS voltage has been .73 as long as I've owned the car and idle position shows 0.0% at idle. It has always annoyed me. When I take my foot off the gas it's because I want to slow down, not continue on at 20 MPH.

I always thought it was part of the stall saver routine or I read in the hack about keep alive steps ( KA ). I could never make much sense out of that stuff. Anyone care for a quick lesson?

Regards,
Gary Anderson

 

My '90 SD setup used to do that. If I coasting in gear at 800 RPM and disengaged the clutch the idle would jump up to 1000. And when I came to a stop it went back down.

I decreased the IAC follower steps until it didn't do that anymore. Problem solved. Too few steps and the engine would stall sometimes.

 

Hi,

Well the 730 does recalc tps on startup, so the real only negative effect there would be it goes WOT a little earlier than the blades do. I can reset it to .49 though.

Yeah 730 $8D.

So what are you recommending here, dropping spark advance at
1200-1400rpm at like <60kpa ?

Idle speed timeout steps vs coolant temp?

Thanks!

-- Joe

 

Closed throttle TPS, Spark

22.5
22.5
22.5
27.1 -> 20
25.0 -> 15
29.9 -> 15
35.2 -> 15
35.2 -> 15
35.2 -> 15
35.2 -> 15
35.2 -> 15
35.2 -> 15
35.2 -> 15

25 25 25 25 23 19 19 17 12 6 6 6
25 25 25 25 23 19 19 17 16 12 6 6
26 26 26 26 26 25 25 25 22 17 12 12
15 25 29 29 28 28 28 27 25 22 16 14
15 25 32 32 32 29 29 28 27 25 17 17
15 25 34 34 32 32 32 30 28 27 22 22
15 25 34 34 32 32 33 32 29 28 28 28
15 25 34 34 32 32 35 34 34 28 27 27
19 25 34 34 32 32 38 35 35 30 27 27
15 25 34 34 32 32 36 36 33 28 28 28
15 25 34 34 32 32 36 35 32 28 27 27
15 25 34 34 32 32 38 33 28 26 26 24

On the left hand side is typically how I run the spark table.
Depend on how you have the fuel set you might have some crackling in the exhaust during overrun. If you don't like that, then you'll obviously need to rework that some.