Short/Long Term Fuel Trims...do these look ok?

[kjlindgr]

Hey all. I've got an issue I'm hoping someone can help me with. I have a 2013 Corvette with the LS7 in it. It was perfectly running before with a Mamba intake, Fast 102 intake (stock throttle body) and Kooks longtube and catless 3" midpipe. I since added a relatively mild cam (cam card attached), the necessary supporting springs/retainers, and a Nick Williams 102mm throttle body. Since then, I can hardly keep this thing running. It's running stock cam gears and I have verified the timing and have pictures to prove it's spot on. I measured pushrod length with the EO/IC method and they were really just a wee bit longer over stock which I can believe due to the mild nature of this cam. I'm ruling out most of the mechanics of the install and am now leaning more towards the tune.

Here's what I did. I am shooting for a MAF only tune at this point, but I followed the E38 tuning guide to disable DFCO, and closed loop O2 control. The car would start, and idle (kind of), but when I blipped the throttle, the tone would change to indicate it was clearly cutting cylinders, it would stumble and then die. What I found is that it was pretty consistently flooding out cylinders 3, 5, 7 and 4. I tried pulling out a bunch of fuel from the MAF table but that didn't help too much.

Then, I turned back on the STFT and LTFT adjustments and noticed something I believe is a bit weird...but that's why I'm asking. Right away, it looks like it is trying to pull fuel from bank 1...which I assume to correct the reason plugs 3, 5, and 7 were wet. And it's looking like it is adding fuel to bank 2. Log attached. The car is stationary, idling, and the areas where I apply throttle is a slight roll-on, hold, and release. I checked the intake for leaks, but everything looks and seems tight. No whistling, odd noises, or anything.

Let me know if this looks "normal" for an idle condition. What strikes me as odd perhaps is that between the banks, there is at times a 15-20% difference in fueling. I had read that you can't believe trims at idle and they really only apply when driving, but that's just what I read. The issue I'm facing is that if I need a big reduction in fuel at one bank versus the other, how do I ever accurately do open loop MAF tuning?

Any help or thoughts would be appreciated guys.

Thanks!

LTFT look off??
17698


LOG FILE:
17696


CAM CARD:
17697

[joecar]

Are the front NBO2 connectors accidentally swapped bank-to-bank (maybe not)...?

MAP waveform does not look correct... I would expect idle to be at 65 kPa and to go up as throttle is opened.

[kjlindgr]

Thanks for the response joecar. Are the left and right side sensors different? I know the primary and secondary are different, but I didn't know that there was a left and a right. Let me know if that's the case and I'll definitely swap them to check. I didn't touch them for this cam install though but they were definitely out with the header install. Let me know if I misinterpreted your response. I'm not sure what to say about the MAP reading, but I know what you are saying...and I have no idea how to remedy if there is an issue with that.

I have a new shorter log attached with a video link as well. I'm not sure if this issue is related or not. This is when the engine is fully warmed up and it seems to run better. When I blip the throttle, revs go up as intended, but when it comes back down to idle, it goes dead lean, the engine shutters and makes all sorts of funny noises, and then the fuel comes back in and it settles to idle set point. I'm not sure how to keep fuel in this area...or if it even needs to be. I played around with B1829 (minimum idle airflow) but that just seems to leave me with a hanging idle condition as I increase, but I still have this shuttering condition as it settles. Let me know if there are other parameters I should peek at...or if anyone wants to see my tune file.

Here's a screen shot of the issue area and the log file:
17702

LOG FILE:
17703


I will post a link to the video when it's done uploading and all that jazz. Seems to be taking a while on my slow internet connection...

[5.7ute]

Are the front NBO2 connectors accidentally swapped bank-to-bank (maybe not)...?

MAP waveform does not look correct... I would expect idle to be at 65 kPa and to go up as throttle is opened.
X2 strange map behaviour.

[kjlindgr]

Here is the video link I mentioned. I apologize for the horizontal display mixup. I guess my phone had a different plan than I did. It might be hard to tell the noise I'm referring to. There is some squeaking as well, but the car is about 3" off the ground on a lift so that's just the lift arms rattling around a bit.

http://www.youtube.com/watch?v=C-gby_ARjDI

[kjlindgr]

Attached is the tune file if anyone feels inclined to take a peek to see what's going on.

Thanks guys!


TUNE FILE:
17704

[joecar]

Thanks for the response joecar. Are the left and right side sensors different? I know the primary and secondary are different, but I didn't know that there was a left and a right. Let me know if that's the case and I'll definitely swap them to check. I didn't touch them for this cam install though but they were definitely out with the header install. Let me know if I misinterpreted your response. I'm not sure what to say about the MAP reading, but I know what you are saying...and I have no idea how to remedy if there is an issue with that....If the front NBO2 connectors are crossed, then the ECM will cross-trim (i.e. left bank trimming from right bank NBO2, and vice-vera) which causes the LTFT's to diverge (but to a greater extent than what your pic shows).

[joecar]

You changed cam, springs/retainers, and TB...!?

[kjlindgr]

I understand now what you are saying about the connectors. They're tied up in such a way it would be hard to pull them around and crisscross them.

Yes, I only changed the cam, springs,retainers, pushrods, and throttle body.

[joecar]

Also log:
SAE.LAMBDA
SAE.MAF
GM.ETCTP
GM.HO2S11
GM.HO2S21

[joecar]

Is this an E38...?

[joecar]

Looks like ignition timing at idle is wrong (fully warmed up it should be about 18 degrees or so)...

( I'm thinking (from many yearss ago) this may possibly cause MAP to be lower than expected, but I have to research this more )

[joecar]

For the air per cylinder value at idle, it is not following the base idle spark table...

[kjlindgr]

This is an E38 ECU, yes.

I will get you a log of those PIDs you requested soon here. I can change base idle spark if you think that will help a bit. The second log I posted is also a concern of mine. As it is coming down to idle, spark drops, then bumps way back up again and the car starts to shutter and shake. I'm not sure if this is related or not, but also concerns me. I don't want to drive the car if I can't get it to "appear" normal when it is stationary.

Thanks for all your help joecar. I will get that log shortly here.

[joecar]

Leave the spark table alone... the problem is that the ECM is computing the air per cyl incorrectly and/or something is causing it to modify spark advance.

[kjlindgr]

Here's a log file with the PIDs you requested. This is from a cold start to almost hot with no touching of the throttle. At the end, I blipped the gas a few times and it almost died coming back down. I can post a video too I took during that time if it helps see what's happening as well.

LOG FILE:
17707

[kjlindgr]

Here's some videos I took today during the warmup:

Engine bay shot:
http://www.youtube.com/watch?v=uaGu0jqh_PM

Here's a video if it warmed up almost fully, blip the throttle, and it shutters and almost stalls. You can hear the chugging and issues it is having coming down from RPMs:
http://www.youtube.com/watch?v=jqkXH98Npas

[joecar]

If it only happens after you open/close the throttle, it sounds like you may need to look at Throttle Cracker and Throttle Follower.

[kjlindgr]

Correct me if I'm wrong, but I don't think this ECU has a throttle cracker...or at least not one that's labeled as such. In terms of the follower, would you increase the "decrement rate" (B1860)? The description doesn't really help me much to figure out what exactly it's doing. The other thing I could do is lower the throttle follower max MAF (B1604) but I'm not sure if that is something I should mess with. Any help on what to alter?