LSX454 High Idle Issue

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Hello all,

Long time reader/researcher (est 2010) but new to posting. 99% of the time, thru searching on here I find the perfect fix from all the really helpful people on here and go about my business. This time I am struggling and in need of some help. I am attempting to bring the idle down at a stop and in park neutral to a more reasonable level (750ish rpm)on this crate engine installed in a 72 C10. I have gone thru the idle tuning post and just confused myself even more. Attached is a log file of a short drive to see what i am dealing with. Also attached is the tune file. Any input would be greatly appreciated.

[Lakegoat]

It looks like your base running airflow is high. Minus 3.00 from all of the cells up to 1200rpm and see what that does. In other words, where you have 13's, you will have 10's. Under idle rpm, your base is all set to 750, make the maximum 800. It looks like your maf table is low in the lower rpm areas also. Get some stock maf numbers where you have 1's.

[[email protected]]

It looks like your base running airflow is high. Minus 3.00 from all of the cells up to 1200rpm and see what that does. In other words, where you have 13's, you will have 10's. Under idle rpm, your base is all set to 750, make the maximum 800. It looks like your maf table is low in the lower rpm areas also. Get some stock maf numbers where you have 1's.

Thank you for the input I will give that all a shot and report back my findings. For the base running airflow, you are referring to the "Airflow Final Minimum"? I'm not seeing it on there. I'm not very up to speed on the lingo of the table too. lol I really appreciate the help.

It seems odd to me that you would be able to purchase an expensive crate engine like this with a controller package from GM and the tuning isn't correct. I know there is a lot of variables with install but idle speed seems like something they should have pretty dialed in. lol

[Jon S.]

Known issue with the later CPP (GMPP) calibrations - take a look at these threads:


https://forum.hptuners.com/showthrea...-ls3-high-idle

https://forum.hptuners.com/showthrea...e-stuck-850rpm

[Lakegoat]

Thank you for the input I will give that all a shot and report back my findings. For the base running airflow, you are referring to the "Airflow Final Minimum"? I'm not seeing it on there. I'm not very up to speed on the lingo of the table too. lol I really appreciate the help.

It seems odd to me that you would be able to purchase an expensive crate engine like this with a controller package from GM and the tuning isn't correct. I know there is a lot of variables with install but idle speed seems like something they should have pretty dialed in. lol

Engine---Idle---Airflow---Base Running Airflow---Airflow Final Minimum

[[email protected]]

Thank you Jon. I think part of the problem is I was searching specifically for the LSX454 in case it was something different due to displacement. The theory would be the same I'm sure. I neglected to chase it down that path. I will look into that as well.

Thank you for clarifying Lakegoat. I'm better with the Gen3 stuff, I get a bit lost on the Gen4's

[Jon S.]

GMPP (now CPP) has used OS 12638778 in their E67 controllers since around 2009 or 2010.

Originally you could fully adjust the electric cooling fans, and the base idle RPM, using tuning software.

It seems that few years ago, GMPP changed a few parameters that are not available in tuning software. One of these is the base idle RPM, the other is the ability of the cooling fans to cycle on and off while the vehicle remains stationary.

If you use an older version of this operating system (OS) you should have full control of the idle via tuning software.

[[email protected]]

GMPP (now CPP) has used OS 12638778 in their E67 controllers since around 2009 or 2010.

Originally you could fully adjust the electric cooling fans, and the base idle RPM, using tuning software.

It seems that few years ago, GMPP changed a few parameters that are not available in tuning software. One of these is the base idle RPM, the other is the ability of the cooling fans to cycle on and off while the vehicle remains stationary.

If you use an older version of this operating system (OS) you should have full control of the idle via tuning software.

Jon, is there a specific OS that you would recommend I default back to? Would 12632176 from an 09 CTS-V work? Would I need to license another tune file?

[Jon S.]

You can’t completely change the OS in a GMPP E67 (or any E67) using only tuning software.

If you try to flash over the GMPP OS with a CTS-V OS using tuning software, you will likely permanently corrupt the ECM.

There is nothing wrong with the GMPP OS. What the threads that I linked in post #4 highlight, is that if you need to reduce the forced (by GM) minimum idle RPM of a more recent GMPP E67, simply flash it with an earlier version of the same GMPP OS, then retune as is necessary.

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Right on, thank you Jon. Now to try to find an earlier version. There isn't anything on the repository that I can find.


The more I deal with these Gen4's.....the more I like cable throttle Gen3's... lol

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Engine---Idle---Airflow---Base Running Airflow---Airflow Final Minimum

18-12-15 17-46-04.hpl1972 C10 LSX454 Canada Gary Trial 10.hpt1972 C10 LSX454 Canada Gary Trial 11.hpt1972 C10 LSX454 Canada Gary Trial 12.hpt

So started trying to make changes recommended here and other places on the forum recommending other points. Didn't make any progress in any sort of positive direction. Lower airflow table numbers, raises idle so I go the other direction. Add airflow table numbers, throttle percent changes but no drop in idle. Pull timing, no change. Combos of both, no change. The only change that had a slight effect that dropped the throttle percentage caused horrible bucking and hunting in gear (programmed as a manual but using an external TCI controller for the trans) Used some scanner templates I found in another idle thread to help with data logging and half the data points don't display. Attached is some of the fiddling I did. Wasted 3 hours there to load the exact file back into the truck that was in when I arrived. This is so frustrating..... Nobody has come up with a fix for this or even a direction? Every thread I find has recommended fixes then it just goes silent with no updates or actual confirmed fixes.

Another thing I noticed is that the controls in the Scanner to set throttle percent, idle RPM, or timing do absolutely nothing. I turn off the adaptive idle and then it starts to surge and even after turning it off, it never regains control. I have to clear the DTC's to reset everything for it to idle without throttle input after that.

[Pekka_Perkeles]

So started trying to make changes recommended here and other places on the forum recommending other points. Didn't make any progress in any sort of positive direction.

Again, as some have already posted, you NEED to do full reflash with GMPP 430 controller file (and before that license it).

After that just compare it with your original tune and make changes as you wish.

You can easily find the GMPP 430 file by just searching with "GMPP" in the tune repository.

Btw, here in the left is yet another GMPP 525 which didn't idle below 850 and on the right info about the tune it has now. And ran 650 rpm...

gmpp_stock_ls3gmpp_to525_gmpp.jpg

[[email protected]]

Again, as some have already posted, you NEED to do full reflash with GMPP 430 controller file (and before that license it).

After that just compare it with your original tune and make changes as you wish.

You can easily find the GMPP 430 file by just searching with "GMPP" in the tune repository.

Btw, here in the left is yet another GMPP 525 which didn't idle below 850 and on the right info about the tune it has now. And ran 650 rpm...

gmpp_stock_ls3gmpp_to525_gmpp.jpg

This is an LSX454, not the crate LS3's you are referring to. Would this still apply?

[Pekka_Perkeles]

Yes.

[[email protected]]

Yes.

Thank you very much for the help. I will give this a shot and report back my findings.

[[email protected]]

So it finally looks like we have resolved this one. Loaded the LS3 430hp entire file after licencing. Changed nothing and ran it. Hard to start but once it was running and the throttle was able to settle, it idled at the commanded RPM (750rpm) with no surging or hunting. Ran ok out driving but would die in slow speed on-off throttle maneuvers as I figured it would. I then took the "stock" LSX454 file and copied over all differences in the engine tab but the idle speeds I wanted. Started and ran but now it developed a surge at idle with no input to cause it. Reverted back to the LS3 file, changed MAF calibration and all fuel settings to mimic the LSX454 calibration. Would not start without throttle input but once running it ran fine. I then changed start up spark, minimum spark and start up airflow to the tables exactly from the LSX454 calibration. Starts well, runs well, idles at the commanded RPM (seemed to like 800RPM best in gear) and no issues on the shake down drives it has been on so far.