adambros

iTrader: (2)

Okay, so im thinking i need to adjust my TBI unit to allow more air past the blades at idle. I loosen the two screws affixing the tps, give a few turns on the idle adj screw, then rotate the tps to bring it back to ~.54v. However, in order to tighten both screws down the tps must be at its original position.

Is there something im missing here

dimented24x7

iTrader: (2)

Some tps' arnt adjustable, mainly because theres no need for them to be. As long as its around .6 V or so its fine. The ecm automatically self calibrates.

adambros

iTrader: (2)

i got that -- however I'd really like to see my IAC steps around 3-10 at idle (@ normal operating temp) as opposed to 40-70. This requires that I adjust my idle stop screw in -- which in turn raises the tps voltage (blades are more open) -- which in turn makes the ECM think im on the gas.

If I were to leave the tps alone and adjust the Idle stop -- I end up with a tps value of close to 3.2% -- the ecm no longer sees this as idle, and my idle speed is close to 1500rpm.

BronYrAur

iTrader: (1)

I've adjusted the idle stop screw without changing anything with teh TPS. You're turning the screw too much, usually only a very slight adjustment of the screw goes a long way. That, or your fueling or timing is off far enough that you need more turns...what's your setup?

dimented24x7

iTrader: (2)

Whats the raw voltage? Did you try shutting down and restarting? That will allow the ecm to recalibrate itself. I think itll recalibrate to just about any value and regard it as being closed throttle. But, if its too high itll set a code.

adambros

iTrader: (2)

ok, that may be -- i was just trying out what Grumpy had suggested here . . .
basic setup :
350 SBC .30 over, Edelbrock Performer aluminum heads, Comp Hyd. Roller Cam 218/224 112 LSA, Speed Pro Hyperutectic pistons, 10:1 CR, Edelbrock Performer intake, 2bbl TBI 1-13/16" bores w/BBC injectors @16psi, coated Edelbrock headers, 3" exhaust.

adambros

iTrader: (2)

no -- I didn't try shutting down and restarting . . . I just kinda kept an eye on values as I was adjusting -- but never rebooted. I'll try that next. Thx.

BronYrAur

iTrader: (1)

That's a pretty serious setup, are you tuning your Prom? I hope so. If not what are you running for a chip? What's your base timing set at too?

adambros

iTrader: (2)

yes, I'm tuning myself -- well with the help of the DIY PROM board. I gave up on Ed Wright getting the tune down after I got a little schooling in PROM burning. Currently that setup is tuned via a PROMinator Pro, TunerCat, and RT TunerPro, WinALDL and a WB02 (passenger collector).

I've never messed with the timing, 0*d is where it ran best.

dimented24x7

iTrader: (2)

Id shoot for 15-20 IAC counts. There may even be some limits imposed by the stock code for how low the counts can go. You may just have the throttle open too far, hence the high idle. 3.6% tps as reported by the ALDL isnt that far off from closed position. Its probably around .8 V. Not ideal but the computer should still see it as closed throttle and it shouldnt set a code.

BronYrAur

iTrader: (1)

Cool, you got the right equipment. What is your target idle set at? Why did you want to change the screw position in the first place, did it have a bad idle?

BronYrAur

iTrader: (1)

I just looked at the .bin for my car and there's a constant in Prevost's ecu file called "TPS% threshold for idle adjustment" and stock its at 1.96% TPS, so if its registering 3.6% maybe it isn't in idle anymore if that's what that threshold means.

adambros

iTrader: (2)

My first few 'Fastchips' were set at 800 for target idle. Stock for was 600 . I've found a nice median at 700.

I wanted to adjust my IAC steps down, that is why I needed to adjust the idle stop.

adambros

iTrader: (2)

Dim,
yep -- I was able to to adjust the idle stop screw and tps with the Key On / Engine Off. Then disconnected the battery for a moment. Hooked it back up and TPS read -0.7% @ .54v. Thx for the suggestion.