High Idle - 5.3 resleaved to 6.0

[x2xplaguex2x]

Hello, - E38 ECM

I'm having an issue where after the engine was resleaved to a 6.0, the idle is very high when in park. Around 1500-2000RPM. But when I put it into gear, the idle comes down.

When looking at the log, it's desired throttle position is 27, but when you put it into drive, the desired throttle position goes to about 17, and it idles normally.

Also, some times when in Park it will idle normal, but if you just barely touch the gas and let out, it's desired throttle goes to 27, and never comes back down.

the park nutrual drive position wires are not hooked up to the TCM, but i've not had these hooked up before and its not been a problem. Transmission is a 4L60

Tune and log attached, in the log if the idles high, just know it's in park. and when it's around 800, it was shifted to drive.

Thanks for any help.

[x2xplaguex2x]

After some reading in some other post's it looks like this was an issue on some E67's where an GMPP tune file was used an an entire write was done, and then rechanged, does anyone know if there is a similiar issue with the E38 ?

Thanks

[x2xplaguex2x]

Something I also found out, Texas Speed lost this customers computer and replaced it with another one they had. I have a feeling this is playing a role in the issue but not quite sure how.

[Twisted Pavement]

Were there any other mods done to the engine? Bigger cam, heads reworked etc? MAF sensor same? Injectors same? throttle body diameter still the same? I?ll pull up your tune tonight and guess along with you. The clue might be your desired throttle angle you mentioned. Park/Neutral (idle with no pedal input) have their own tables under Engine>Airflow>Idle, and Engine>Spark>Idle. Bear with me here, going off memory without tune open. But st least you can look at the tables and see if your numbers are below what you logged at idle.

[x2xplaguex2x]

Were there any other mods done to the engine? Bigger cam, heads reworked etc? MAF sensor same? Injectors same? throttle body diameter still the same? I?ll pull up your tune tonight and guess along with you. The clue might be your desired throttle angle you mentioned. Park/Neutral (idle with no pedal input) have their own tables under Engine>Airflow>Idle, and Engine>Spark>Idle. Bear with me here, going off memory without tune open. But st least you can look at the tables and see if your numbers are below what you logged at idle.

Only thing different was the intake, it was an LS2 style intake. Everything else the same, except it was resleaved to a 6L


Unfortunately this truck is about 6 hours away, so it'll be unlikely I can do any further testing with it.

[Twisted Pavement]

Just wrapping up for the night, there looks to be a few opportunities for improvement in the tune, but to get you started, here is a few things to look at first. Up front, I'm not a pro like many of the folks on here, though, I do go full geek on this stuff. Anyways, hope this helps.

under Engine>General>Cylinder Volume the cylinder is set to .70819=5.6L. Needs to be set to 0.750 (if it is a 6.0L). This will let the engine know how much air it is pulling in at a given RPM, and keep it from fighting what it expects with RPM/MAP tables or MAF readings. Cylinder Air Mass etc come from this Cylinder Volume value. give me a hall pass if you are already down with this info. Just sharing what I have seen in my handful of experiences. This number needs to be accurate. Gen III and Gen IV engines depend on measured airflow for pretty much everything.

*Engine>Idle>Airflow>Airflow Final Minimum is pretty high across the board for an OEM Cam 6.0L. I just referenced against my OEM L92 6.2L in my 08 H2, it is closer to 6-7g/s through 600-1000 rpm area. Ramps up gradually from there. I just checked against my buddy’s 07 Tahoe 5.3 and e38 (bolt-on’s only) we tuned this weekend, it is closer (slightly lower) to the H2’s numbers on the same table.

*Take a look at your Engine>Startup>Idle P/N has some strange looking shape to it 20-44 deg area. Not a smoking gun, but can get rid of an issue, before its an issue. Well, unless there is a reason for those values.

*Engine>Idle>Airflow>Startup Airflow table is pretty high. Tahoe 5.3 doesn’t have the table, H2 6.2L has same, but about 30-40% lower on the 6.2L than the table you posted. That is really only referenced for lighting off the engine tho. Might look at this if you’re having trouble starting up.
*in gear looks normal for the (reused/OEM cam?)

*just an observation, during the log you posted I see the Pedal Position stays near 13.9% then gradually tapers off over the length of the log. Not sure where the controller pulls the spark able and idle speed from if the pedal is not at zero. During playback on my laptop, I see your channels list, but my gauges/graphs/Time shows. my gauges logs the generic Accelerator Pedal Position. shows 0-100 consistently on everything I plug into even my 18 Camaro. this could be me not understanding the software, but if nothing else, it was something that was different than the other rigs I have tuned on. Maybe log that channel on your end. See if there is a bad ground on the pedal? just ideas.

well, im going to wrap up my 18 hour day. hope something here is useful. good luck and please do post up if you find anything.

[Twisted Pavement]

I had one other thought this morning about your idle. I checked your tune last night and saw your ETC Scaler was pretty normal against the only other 5.3L e38 I have (2007 Tahoe), and it was spot on, so I kept moving. This morning it occurred to me that you may have swapped the throttle body when you got your LS2 intake. If it is updated/increased, that would create a few issues on a Gen IV trying to reach commanded airflow. My limited experience with Gen III cable TB?s... not sure on those.

[Twisted Pavement]

Blowing up your thread here, but last thing - the 08 H2 with the 6.2L I referenced runs an e38 ecm. Those are the only e38 tunes I have in my laptop. I have a couple e67 tunes, but trying to keep it apples to apples.