LS2 E40 PCM driving me nuts....startup issue and 1400rpm buck....all else is good

[quik95lt1]

Looking for a bit of help here.....Car is a 06 GTO M6 with LongTubes Hi Flow Cats, Catback, Ported FAST 90 and a 226/234 .600/.600 112+3 cam..............ive got the car idling great at 900rpm and it drives around great except for two issues...........first issue is i cant seem to get it to fire up on its own.....ive got to hold the accelerator for the first 2-3 seconds at like 2000rpm then if i let it go its perfectly fine could be 40* out or 80* and the car could be ice cold or hot it doesn't matter.......if i start it without helping it runs fine for a second then surges and stalls.......second issue is a pesky buck from 1300-1600 it only occours at very light throttle (.18g/cyl area)........yet the car will put along at 1100 rpm just fine so i know its a tune issue..........i had the buck gone before but i had to richen the VE table in the 1600-2400rpm area and after i did this the car bucks.........ive tuned quite a few LS1's with much more agressive cams than this and not had these issues....the E40 PCM is apparently quite different and more complex than the old LS1 computers so any help here would be great.......i seem to be pretty close i think......i have attached my current tune file to this post.......as well as a short data log from driving in traffic where you can see the buck

Thanks!!!!!
Mike

[joecar]

Hi Mike,

Yes, the E40 is different, but it still has many of the old tables.

In your .tun file, the open loop commanded fuel tables are all set to EQR 10 (AFR 1.5), this is way wrong, they should be at EQR 1.0 in the no-load areas.

[joecar]

Base idle spark is too low.

High octane spark can probably be higher than 20 in the high load plateau, altho the slope getting there looks a little too steep (to me).

[joecar]

And welcome to the forum :cheers:

[quik95lt1]

Hi Mike,

Yes, the E40 is different, but it still has many of the old tables.

In your .tun file, the open loop commanded fuel tables are all set to EQR 10 (AFR 1.5), this is way wrong, they should be at EQR 1.0 in the no-load areas.

thats what i thought!!! but the stock tables show the same thing too odd no?


Base idle spark is too low.

High octane spark can probably be higher than 20 in the high load plateau, altho the slope getting there looks a little too steep (to me).

yea im going to do the WOT spark after i get the drivibality done........


And welcome to the forum :cheers:


thanks!!!!! and i appreciate the help!!
:D Mike

[quik95lt1]

think i made some good headway at lunch time today..........bucking is almost gone..........i can putt along in first gear at idle smoothly...........and the startup is much much better.........starts bogs once then catches itself.........im getting closer....now is there anyway to lean out my idle without affecting the numbers in the VE table?? i need to lean my idle out at 900rpm but i dont want to affect tip in on the throttle........heres my newest tune.......