LQ4 single turbo e85 cannot make it idle... Help..

[carlsonauto]

Ok I have a 2004 lQ4 6 litre that I put in my 94 OBS 4x4 truck. I have it all working happily (well its getting there) except no matter what I do I cant seem to make the dumb thing idle. I have searched and read and searched some more and I have done everything I can find and think of to make the thing play nice. Its just crabby about life and nothing I do seems to make it happy... I have done lots of things that have made huge improvements but its just not right. The cam isnt even that crazy, I cant believe its giving me this much trouble. A little info about the combo im running.. The cam is a comp 54-444-11 (224/230 duration on a 114 lsa) It has an aluminum aftermarket ls1 style intake, 102mm throttle body, the pcm and harness were originally out of a 2003 silverado 5.3 4x4 its converted to DBC and SD using 04110003 OS and a base tune from a 2004 GTO. Another thing, the 102mm throttle body that I am running was not a name brand unit and it originally only had about a 1/4" passage from the IAC to the manifold vacuum side of the throttle blade, needless to say that made the effectiveness of the IAC stop at about 40 steps so I looked at a factory throttle body and its passages everywhere are huge as I suspected. I took it upon myself to put it in the mill and rectify the problem. I did measure all the other dimentions of the IAC opening (depth, diameter, main passage opening etc) just to make sure that all else is correct and It is all within .010". I put it all back together and the IAC actually does something in the higher counts now. I also have the "flex fuel" sensor wired up and plumbed and for some reason that doesnt seem to be functioning either.. If anybody has any ideas or a "miracle fix" for either issue I am all ears. Its probably something obvious so here is my current tune that I am using to "auto-tune" my VE tables with. blue truckAUTO-VE.tun thank you in advance...

[bmax]

B4603 looks low. Have you done the RAFIG process. I would start there.



Brad

[carlsonauto]

I have not, I cant get it to idle long enough to log anything...

[carlsonauto]

this may be a dumb question but if I set the idle (in the tune not on the tb) to say 1000 rpm and datalog to get the RAFIG will the numbers be off be off because of the different rpm?? I am assuming so, thats why I have not done that either......... although it may get me close enough to make progress...... any thoughts??

[carlsonauto]

ok I reverted everything I had changed back to stock and got it to idle long enough to do the rafig with hopes that that would make a huge difference... not so much.. This thing is making me feel dumb, I made a tbi 383 idle with a way more radical cam and a much dumber pcm, I should certainly be able to get this thing to idle... I kinda have a gut feeling that something is hurt in the engine so I am going to do a compression test in the morning just to rule it out... Assuming its not hurt what should I change first to help it idle better?? I have my own ideas but im very much open to suggestions...

[macca_779]

Add 5 grams to desired air across the board to get it running and go from there. It's difficult to tune something that won't run


Sent from my iPhone 4 using Tapatalk

[carlsonauto]

ok I am pretty sure I figured it out... it wants to idle in the extremely lean end of the spectrum... I had tried playing with the V/E table before but stayed in the low 12 to high 13 range at idle because I have never seen an engine that wants to idle higher or lower than that it actually seemed happiest toward low 12's.... just for the heck of it I decided to make the V/E table flat from 400-1200 rpm and from about 30 to 75 kpa range and kind of a lot lower than I thought it should be.... (wend off gut and burning eyeballs) wideband read 14.5-high 15 even low 16s at times but the stupid thing idles about 98% better.. I tried recalibrating the wideband because that cant be right (right??) but no change.. must have something to do with the wideband 02 placement in the downpipe or omething crazy like that.. I cant imagine its actually correct...

[joecar]

B3647 and B3649: all those cells with value 1.00 EQR will cause the COS to STFT trim to stoich... i.e. the PCM will trim ahead of you regardless of your VE edits

( this is a feature of the COS's, in OL any cells in B3647/B3649 that are at stoich will cause STFT trimming... it's called semi open loop (SOL) ).


In your case it looks like you're using only B3647.

[joecar]

Also: between B3647 and B3618, fueling is not sufficiently rich for any significant load.

[carlsonauto]

guys thanks for the replies, joe as far as the B3647 and B3649 go I am a bit confused as to what they do.... Is that where the GM.AFR pid gets its input from?? I have been watching that on my logs and wondering if i can and how to change that. Are you saying that no matter what I do with the v/e table its going to keep going rich if I dont change B3647??? It seems (in my head) that regardless of what B3647 says I should be able to manipulate it however I want with the V/E table, even though thats becoming apparent that that is not the proper way to go about doing it.. That brings me to my next question... What is the proper method?? If im seeing and understanding this correctly (and I very well may not be) table B3647 is basically just a mutiplier of sorts to the V/E table correct?? Also I would love to be using the B3649 table, I have the "flex fuel" sensor all wired in and plumbed and unless I am missing something in the tune I believe it should function, however the pid for ethanol shows 0% all the time and im at least 70% am I missing something here too?? sorry for all the dumb questions but it has been 7 or 8 years since I drove around in this thing pushing buttons on the laptop and that was with tunerproR/T on a TBI 383.... EFI Live on an Ls pcm is a bit more complex but I know if I could make that dinousaur pcm play nice I can certainly handle this.. in time..