TPS causing throttle hang?

[steveo]

a test... what if you drop 100rpm off desired idle, does actual idle drop 100rpm too? that'd confirm it's at least in closed loop idle control when this is occuring

[RobertISaar]

FWIW, the 60V6 MPFI code will bump up idle speed if it sees low battery voltage, but it will be reflected in the target idle speed, not in a "raw" manner like IAC counts. i would expect newer code to do the same.

[1BadAction]

Alternator voltage looks a little low, have you got the AC on and blower on full blast maybe?

Yes, fans times 5 actually . Tahoe Efans AND factory trans cooler fan on PWM at 85% plus the AC front and rear on full blast. Temp was 104 degrees here at DFW when that screen cap was taken. It is a 105 amp alternator but I am looking into getting a 155amp. That said, even with the voltage higher it exhibits this same behavior. I believe similar masks start compensating for battery voltage at 11.8 volts.

yeah, looks normal by the dashboard? but there may be conditions in the code where the 'idle' bit is set to 1 but it's still going open loop idle, not following the idle target, and it's just advancing a fixed number of steps, that seems to be what's going on anyway...

maybe it is a battery voltage thing? 12.1 might be in the range of 'oh crap, there's a bunch of battery voltage... lets add idle speed'?

is there any disassembly for this mask? (dont even know what mask it is, you haven't told us)

Mask is $D8 from a 1991 454ss. 7060 ECM.

After reading your post I got curious and dug back into the BAMY Hack...
;---------------------------------
; IAC GAIN
;---------------------------------
L85D9 FCB 1 ; Closed Loop PERIOD MULT, SMALL ERROR RE-TRACT
L85DA FCB 1 ; Closed Loop PERIOD MULT, LARGE ERROR RE-TRACT
;
L85DB FCB 1 ; Closed Loop PERIOD MULT, SMALL ERROR EXTEND
L85DC FCB 1 ; Closed Loop PERIOD MULT, LARGE ERROR EXTEND
;---------------------------------

Factory is 1 second delay to OL in this bin, I have it set to 255 seconds (so it stays CL in traffic) I think this may be my problem. If it is I'll add it to the XDF and see if I can get my delay to work correctly. If not I'll live with the OL idle.

[Fast355]

Yes, fans times 5 actually . Tahoe Efans AND factory trans cooler fan on PWM at 85% plus the AC front and rear on full blast. Temp was 104 degrees here at DFW when that screen cap was taken. It is a 105 amp alternator but I am looking into getting a 155amp. That said, even with the voltage higher it exhibits this same behavior. I believe similar masks start compensating for battery voltage at 11.8 volts.




Mask is $D8 from a 1991 454ss. 7060 ECM.

After reading your post I got curious and dug back into the BAMY Hack...
;---------------------------------
; IAC GAIN
;---------------------------------
L85D9 FCB 1 ; Closed Loop PERIOD MULT, SMALL ERROR RE-TRACT
L85DA FCB 1 ; Closed Loop PERIOD MULT, LARGE ERROR RE-TRACT
;
L85DB FCB 1 ; Closed Loop PERIOD MULT, SMALL ERROR EXTEND
L85DC FCB 1 ; Closed Loop PERIOD MULT, LARGE ERROR EXTEND
;---------------------------------

Factory is 1 second delay to OL in this bin, I have it set to 255 seconds (so it stays CL in traffic) I think this may be my problem. If it is I'll add it to the XDF and see if I can get my delay to work correctly. If not I'll live with the OL idle.

That is some draw, very similar to what I am running in my 97 Express Van. I would suggest something more than 155a when you upgrade. I went from a 140a CS-144 to a 200a AD-244 in the Express to run a very similar setup. I actually have not driven it in a couple of weeks, burned up a cooling fan motor and have not had the time to change it yet. Been having too much fun driving the Titan anyway after tuning it for the headers.

[1BadAction]

That is some draw, very similar to what I am running in my 97 Express Van. I would suggest something more than 155a when you upgrade. I went from a 140a CS-144 to a 200a AD-244 in the Express to run a very similar setup. I actually have not driven it in a couple of weeks, burned up a cooling fan motor and have not had the time to change it yet. Been having too much fun driving the Titan anyway after tuning it for the headers.

Well, keep in mind the TBI style Alternator, they're different than what you're running. Not sure if the AD-244 will fit the bracket.

Either way I'm going to search around before I drop the hammer, I've survived with it this summer so far and not in a huge rush. When I do the alternator I want to go ahead and swap to my cast iron serpentine brackets and aluminum intake (that doesn't have the support boss for the stamped steel brackets).

[Fast355]

Well, keep in mind the TBI style Alternator, they're different than what you're running. Not sure if the AD-244 will fit the bracket.

Either way I'm going to search around before I drop the hammer, I've survived with it this summer so far and not in a huge rush. When I do the alternator I want to go ahead and swap to my cast iron serpentine brackets and aluminum intake (that doesn't have the support boss for the stamped steel brackets).

I have seen CS144 and AD-244 alternators put on TBI 350s with stock brackets and sight modification to said bracket. Most drill a larger hole and add a fender washer to stabilize the larger bolt of the AD-244. My 1980 Corvette has a serpentine setup from a 1991 Firebird TBI 305 and the CS-144 from my Express and all I did was add a length of aluminum tubing inside the bolt hole of the alternator as a bushing for the smaller diameter bolt rather than drill the bracket.

[1BadAction]

I have seen CS144 and AD-244 alternators put on TBI 350s with stock brackets and sight modification to said bracket. Most drill a larger hole and add a fender washer to stabilize the larger bolt of the AD-244. My 1980 Corvette has a serpentine setup from a 1991 Firebird TBI 305 and the CS-144 from my Express and all I did was add a length of aluminum tubing inside the bolt hole of the alternator as a bushing for the smaller diameter bolt rather than drill the bracket.

Sounds a bit easier than I anticipated I was thinking the pulleys would be out of line, or the clocking might not be available, etc... Might see what I can find in that case because I'm not a big fan of leaning on an alternator to near 100% of its capacity as much as I am.

[1BadAction]

After reading your post I got curious and dug back into the BAMY Hack...
;---------------------------------
; IAC GAIN
;---------------------------------
L85D9 FCB 1 ; Closed Loop PERIOD MULT, SMALL ERROR RE-TRACT
L85DA FCB 1 ; Closed Loop PERIOD MULT, LARGE ERROR RE-TRACT
;
L85DB FCB 1 ; Closed Loop PERIOD MULT, SMALL ERROR EXTEND
L85DC FCB 1 ; Closed Loop PERIOD MULT, LARGE ERROR EXTEND
;---------------------------------

Factory is 1 second delay to OL in this bin, I have it set to 255 seconds (so it stays CL in traffic) I think this may be my problem. If it is I'll add it to the XDF and see if I can get my delay to work correctly. If not I'll live with the OL idle.

This was it, changed the open loop delay to 1 second and it works as it should work. I don't even think I'm going to try to make the delay work, it runs fine in OL. Thanks for the help and suggestions guys, I doubt I would have looked at this myself.

In other related news, you can balance a nickle on the air cleaner of a 454 BB Chevy as it's idling in open loop.

[lionelhutz]

I'd expect that is delay between when the %TPS drops below the idle threshold and when the PCM goes to closed loop idle. It makes absolutely no sense to be closed loop idle for 1 second and then go to an open loop idle.

That idle flag on the dashboard likely just tells you that the %TPS is below the idle threshold and not that it's in closed loop idle.

[1BadAction]

I'd expect that is delay between when the %TPS drops below the idle threshold and when the PCM goes to closed loop idle. It makes absolutely no sense to be closed loop idle for 1 second and then go to an open loop idle.

That idle flag on the dashboard likely just tells you that the %TPS is below the idle threshold and not that it's in closed loop idle.

These bins are open loop idle, from the factory. BAMY, BAMT, AWWH, etc. put a data logger on a bone stock 1991 454ss or 91 454 Suburban and it will be in open loop as soon as it's back to an idle and the truck is not moving.

I've tried to make the idle work in closed loop in multiple ways (using the delay to keep it in CL, changing the rpm to enable open loop parameters, tps settings, etc) Whatever way you do it, these 7060 454 bins do not like to idle in closed loop. There is always some quirk, like this throttle hang, hunting idle, and so on. Change it back to open loop idle and it's perfect.

Closed loop idle just doesn't want to work with this mask and these bins, and after finally giving up and changing it back last night, I'm 100% fine with that.

[RobertISaar]

closed loop IAC control, not closed loop fuel control.

[lionelhutz]

Ya, I'm talking closed loop IAC control, not closed loop fuel control. Obviously, the throttle hang is caused by open loop IAC control using some open loop table or scalar. The code snippet appears to point to the I gain of the IAC control.

[1BadAction]

Ya, I'm talking closed loop IAC control, not closed loop fuel control. Obviously, the throttle hang is caused by open loop IAC control using some open loop table or scalar. The code snippet appears to point to the I gain of the IAC control.

Hmm. I see. I was not aware of the IAC having an open loop setting.

This explains a bunch. I wonder if bumping the "stall saver" will add a set amount to the IAC? Right now it seems to be correct most of the time... but has done it once or twice.

At any rate, I'm going to start with a fresh bin and copy-paste all of my fuel/spark tables over to it, then see what it does. I've saved and resaved this same bin on dropbox so many times between my work machine and my home machine, it wouldn't surprise me if something is wonky.