Sudden death

[horsepowerguru427]

2002 Trans am
LS2(sbe) 235/248 .649/615 111 LSA, 109.5 ICL
Ls3 heads (0823) LS3 intake
102mm Throttle body
FIC LS3 42lbinj
6speed
Open loop SD

Ok people smarter than I am, Ive been working on getting this thing to idle and come back to idle without dying or having to give it pedal. Mainly remapping the IAC steps vs effective area table at the moment. Ive got it idling pretty well and not falling on its face or sputtering out and dying. However, it seems not long after i hit 180 ECT it just DIES. When it happened during the first log it caught me off guard and it died. Log 2 I was expecting it and gave it a small throttle blip and it came back to idle and everything was fine. A few min later the idle became irratic, tried to recover and it died.
IAT base correction pulling timing?
Any thoughts?


Both logs are "cold starts"

[edcmat-l1]

Put it back in closed loop. Put most of the idle settings back to stock. Your IAC counts look good but the idle trims are adding a bunch of air. This is probably because you got the IAC position vs airflow goobered up.

Your BRAf doesn't look right. Cold it's too low, warm/hot it's too high. And it dips at 46*F. That makes no sense.

If you're coming up with numbers that don't make sense and are that far away from normal, you got something jacked up somewhere.

[Alvin]

There are so many changes that do not make sense.

Keep it real simple and only change the things you fully understand. I might change 1/3 of the tables you did on this.. Less is more.

[bk2life]

102mm Throttle body

what brand?
what sensors?

[horsepowerguru427]

Put it back in closed loop. Put most of the idle settings back to stock. Your IAC counts look good but the idle trims are adding a bunch of air. This is probably because you got the IAC position vs airflow goobered up.

Your BRAf doesn't look right. Cold it's too low, warm/hot it's too high. And it dips at 46*F. That makes no sense.

If you're coming up with numbers that don't make sense and are that far away from normal, you got something jacked up somewhere.

BRAF numbers that have been changed from stock number came straight from the logs i posted. Hasnt been colder than 70F so i havent gotten much cold idle data at the moment. The IAC vs airflow table- I have a formula for recalibrating the IAC steps based on error %. Its helped idle a lot better and return to idle, however, i agree that the IAC step curve is very wonky looking.

There are so many changes that do not make sense.

Keep it real simple and only change the things you fully understand. I might change 1/3 of the tables you did on this.. Less is more.

I didnt realize the OS was still for a truck, Ive been working with the file that came in the car. I just looked it up in repository and its a truck OS. The values that you guys are saying do not match and shouldnt have been touched came from a stock 2002 ws6 6spd tune. Ill post the tune im referring to.

what brand?
what sensors?

Stock sensors (ac delco) Velocity throttle body. It was on the engine when i got it. I plan on replacing it in the near future. Just wanna get it easier to drive for now. Its hard to drive a 6spd that doesnt wanna idle lol

-EDIT- I just double checked and the OS in the Trans am matches my all original 2002 Z28 OS

12212156

However, this number only comes up as a truck OS in the repository....
I thought i started over with a new file on this trans am based on my camaro awhile back, had me a little confused...

[edcmat-l1]

The IAC vs airflow table- I have a formula for recalibrating the IAC steps based on error %. Its helped idle a lot better and return to idle, however, i agree that the IAC step curve is very wonky looking.

Error percent of what? You shouldn't have to touch that table. It's causing your BRAF numbers to be unrealistic. Put it back to stock. Leave it alone.

[horsepowerguru427]

Error percent of what? You shouldn't have to touch that table. It's causing your BRAF numbers to be unrealistic. Put it back to stock. Leave it alone.

Error of where it is in steps vs where it needed to be. I was under the impression thats how you adjusted for a larger TB on DBC.

Idle Desired Airflow / Dynamic Airflow x ISC Steps
Ill admit ive never tried it before now. I was doing a class about idle tuning awhile back and this is what was recommended for DBC adjustment. It definitely helped at idle. I just want it to be able to drive reliably to get VE data. Its hard to get idle data or decel data when it wants to die everytime it reverts to idle tables.

Youre saying put the table back to stock, re-log a cold start and collect BRAF data with stock IAC step values?
What about IAC Park Pos. Airflow? Leave it stock?

If nothing else this is a great learning experience lol Because i wouldnt have chosen a junky ebay throttle body, nor a 102mm. However, a lot of people do buy this junk, so i figure ill run into messing with one of these before long anyways.

[Alvin]

That isn't correct.

It's describing how the IAC passage flows vs steps.. Well its saying the hole is equivalent to x

You shouldn't need to mess with this unless idle desired airflow goes above 39 g/s for cars or later trucks and somewhere around 28 g/s for early trucks.

Another reason is if you are being really anal and want final idle airflow matches dynamic/maf/VE airflow. Which isn't important.

[Alvin]

Those junky aftermarket throttle bodies aren't a challenge to tune.. they are often not tunable because

the blade doesn't come to the same stop,
the blades fit poorly,
the TPS engagement is loose and causes the TPS to not be consistent.
The IAC passages are also choked up and won't cover the temp range of the engine. You'll often find IAC all the way closed warmed up and idle still high and IAC open all the way cold and not able to achieve idle.

[horsepowerguru427]

That isn't correct.

It's describing how the IAC passage flows vs steps.. Well its saying the hole is equivalent to x

You shouldn't need to mess with this unless idle desired airflow goes above 39 g/s for cars or later trucks and somewhere around 28 g/s for early trucks.

Another reason is if you are being really anal and want final idle airflow matches dynamic/maf/VE airflow. Which isn't important.

I see. Thank you for the clarification on that! Ill start over...again lol

[horsepowerguru427]

Those junky aftermarket throttle bodies aren't a challenge to tune.. they are often not tunable because

the blade doesn't come to the same stop,
the blades fit poorly,
the TPS engagement is loose and causes the TPS to not be consistent.
The IAC passages are also choked up and won't cover the temp range of the engine. You'll often find IAC all the way closed warmed up and idle still high and IAC open all the way cold and not able to achieve idle.

I did pull this one off and locktite the blade screws and install new sensors not long ago. Everything felt good as far as shaft play or blade movement/closing. I could not get it to hold an idle by itself at all even with the blade maxxed open (.76v) So i stepped up the IAC exit passage over the throttle blade. It really wasnt a step up, more of a cleanup. knocked off some corners and edges and helped idle tremendously. A few logs later, this is where im at...

Also, do you normally keep throttle follower and cracker on a cam/tb combo like this? Or just zero it all ? Ive lowered stock values a lot, which helped....

[horsepowerguru427]

Heres another log. "cold start" (its like 90F lol) I reset all IAC values back to the stock WS6 file. Along with BRAF +4g/s across the row. Idle adaptives are still turned off. Other than that its the exact same as the tune i posted with logs.

My questions are:
1. Why is it just dying like that right around 180F- sudden drop in timing AAANNNNDDDD ITS GONE!

2. After it get past that point where it dies suddenly, its fine for a few more min and then it starts surging and oscilating til it just gets out of range and dies.

Whats up with that? lol

You guys got some suggestions from here?

-EDIT- What do you guys think of the idle timing? It would idle fine on 18degees sometimes but i raised it in hopes it would help the stalling issue. Lowered it back down to where it is now because it didnt help significantly....

[horsepowerguru427]

Put it back in closed loop.

You think it'll run on trims? I just figured it was a unanimous vote that with a cam that big OLSD was the way to go. I wouldve kept the MAF if it hadnt been duct taped on with cardboard and RTV lol and a 76mm going into a 102mm tb. It was easier to just remove it.