Hey I've just started burning EPROMS for my TBI 305 that I rebuilt with a low end torque cam.

I'm using the whole computer and harness from a 1990 c1500 truck.

I'm having pretty good luck so far and I'm making lots of improvements.

it runs great and I'm unleashing a lot of power over the stock tune

I'm having an idle problem though, I'm using TunerPro with the 42.XDS definition
and I read the BIN out of my stock chip

when I adjust the table for desired idle speed vs. temp, it seems to only change my park and neutral idle speed.

when I put the trans in drive the engine tries to idle at the stock speed which is a bit too low for this cam I guess

does this ECU have a different table or a modifier or something for drive idle?
I don't see it anywhere in the definition.

hopefully someone can help me out here, I'm having such great luck tuning everything else!

 

I thought there were two tables one for neutral/park and another for drive $42.

Also stall saver table.

 

I'm not seeing them in my list, there's a power steering stall steps added value but I don't have a sensor on my PS system so that doesn't do anything.

I figured there must be another table for drive but I sure as heck can't find it

 

I used $42 some time ago. It may be out of place. Do a search for RPM or Drive and see what shows up. I recall it to be a coolant based table.

 

Is the P/N input to the ECM hooked up correctly? Ground when in P or N, and open when in any drive position.

When in P/N there is no real idle control, just an upper and lower limit. When in drive, then the idle speed table is used.

Hit the Tuning Guide Book sticky and read the "IAC Logic" thread linked in it. The engine coolant temperature and IAC kickdown steps is also important to having control of the idle speed.

RBob.

 

I haven't changed anything from the stock setup so I'd imagine that the switch would be hooked up correctly.

I hope there's a separate table or constant modifier for the drive idle, that makes sense.

I'll try searching for it

are there different versions of the 42.xdf definition? I got mine right from the tunerpro guy

 

ok, I found "7747-mine.ecu" and used that as my definition.

it has a constant called "IAC steps subtracted in drive"

it's at 4 steps. that doesn't seem like much to me but I think I'm going to try making it 0 or maybe even negative.

all my chip burning stuff is at work so maybe I'll head over and try that tonight.

seems weird that some of the different definitions are missing certain things.

does anyone know of a complete definition?

 

also, what the heck is "throttle follower" it's a constant in this other definition file and there's one for p/n and one for drive

 

It adds IAC steps after you blip the throttle. If you decrease that you will return to idle faster.

 

oh, ok that makes sense now thanks.

I solved part of my problem hah. the engine doesn't have a knock sensor and somehow that input on the computer was false triggering and retarding the heck out of the timing making it barely idle.

I hooked up a knock sensor and have it sitting off to the side.

it still seems to idle a tad low in drive.

does the "IAC steps subtracted in drive" mean idle faster in drive or slower?

is it a modifier for the whole time it's in drive or just for a short while after you shift to keep it from stalling when the transmission grabs?

thanks for helping me through this guys