In Drive Stall and Cruize Controling

[joshlarsen]

Hey Guys, Im brand new to tuning and but have been reading around a lot and watching lots of how to videos to try and learn before posting this. I just rebuilt an 2001 LQ4 with the following mods: decent sized cam, flat top pistons, TBSS intake with a 92mm TB, Static fuel pressure of 55-58PSI, 50lb injectors(ACDelco 12613412 same thats in a 2015 6.0), Long Tube headers, and 3in exhaust with Magnaflow mufflers and its in a 83 Chevy C10.

I updated the tune for the injectors and have had the truck idling pretty good. I think I can reduce the P/N Idle Airflow a little to get STIT to 0 but it idles half decent in park or in gear.

I am trying to work on the MAF Airflow vs Frequency table so currently have the following settings changed so I can do that and I still have a little ways to go to get the MAF dialed in then plan to work on VE and will redo MAF and VE again after that.
Feel free to skip reading these and go to The Problem section below for whats wrong as you experienced guys can probably tell whats up by my tune and log file that are attached.
Engine/Airflow/Dynamic/Dynamic Airflow/High RPM Disable = 200rpm
Engine/Airflow/Dynamic/Steady State/"Hi/Lo RPM Thresh" = 200rpm
Engine/Airflow/Dynamic/Steady State/"Hi/Lo MAP Thresh" = 0kPa
Engine/Fuel/Oxygen Sensors/Closed Loop Enable/Ect vs IAT table all set to 283
Engine/Fuel/Oxygen Sensors/Long Term Fuel Trims/LTFT = Disabled
Engine/Fuel/"Open loop / Base"/STFT Open Loop = Disabled
Engine/Fuel/"Cutoff, DFCO"/Deceleration Fuel Cutoff/Enable ECT = 280
Engine/Fuel/"Cutoff, DFCO"/Deceleration Fuel Cutoff/Stall 12000rpm

The Problem:
I have 2 issues. The first is the most annoying and that's that the truck stalls. When I place the truck in gear it will continue to idle just fine and when I'm moving it runs ok but if I back out of the drive way as soon as I come to a stop it dies or if I roll up on a stop sign it will most of the time die unless I hold the break and still give it some throttle. I have messed with adding more spark in my high and low octane tables below 800rpm. I also have bumped the underspeed spark up some which did help some. Are the 2 "Cutoff, DFCO" settings I changes for fuel cutoff causing issues with my stalling?

Second issue is when I'm cruising down a city street at 30mph it will cruise control and continue going at about 30MPH forever. RPMs hang about 1400-1600 and IAC seems to be open to about 150 when its doing it and is at about 60 when idling. I made all cells 1,600rpm and under in the Throttle Cracker Airflow table to 0 thinking that was causing the cruise control and it got a little better but its still an issue.

Any help is much appreciated. I have attached both the last log which is pretty short and the current tune file. In that log if stalled at about 8:31:20 and 8:31:29 again.

[blindsquirrel]

Static fuel pressure of 55-58PSI

...means you no longer have the 2001's fuel rail & pressure regulator? It's been converted to 'returnless', like your injector data is set up for?

[joshlarsen]

...means you no longer have the 2001's fuel rail & pressure regulator? It's been converted to 'returnless', like your injector data is set up for?

Thats correct. I have the fuel rail that came on the TBSS manifold that does not have the vacuum referenced pressure regulator. I am running a corvette style regulator and the injector data is setup for a non referenced regulator.

I'm actually using injector data from one of your tunes found in post. https://forum.hptuners.com/showthrea...efined-version

[blindsquirrel]

Just wanted to make sure!

[blindsquirrel]

You might get better results if you did the VE first instead of MAF first. VE is still used for transients in MAF-only, and your VE is still stock even with all the mods you've made.

[edcmat-l1]

First thing is, all GEN3s HAVE TO HAVE the VE dialed in to run right.

Second thing is, your narrow bands hover at 900 mv so you know it's running on the rich side of stoich continuously. As long as it's running on the rich side of stoich it will have issues coming back to idle. Just putting it back into closed loop should help some.

Third, put it back in closed loop. Turn off your long-term trims. No use in wideband tuning it at part throttle. Use your trims.

Fourth, put it in speed density and dial in the VE FIRST. The VE is bone stock.

Lastly, you can't put these in "MAF only" (high RPM disable) mode like you can a GEN4. They don't work that way.

[joshlarsen]

Thanks for the help. I'll go work on VE and see how that goes.

Third, put it back in closed loop. Turn off your long-term trims. No use in wideband tuning it at part throttle. Use your trims.

I assume by use trims for part throttle tuning I should apply the changes that the ST Fuel Trims graph have to the VE table?

[edcmat-l1]

Thanks for the help. I'll go work on VE and see how that goes.



I assume by use trims for part throttle tuning I should apply the changes that the ST Fuel Trims graph have to the VE table?

Correct. Plot the STFT in a VE histogram and then copy/paste/multiply by.

Make sure it's setup in SD properly. To verify, once it's started check for codes. You need to see a P0103.

[joshlarsen]

I have MAF disabled but a question before I go and modify VE in the wrong direction. The STFT show rich just like the narrowband O2s show but the AFR Err table and Wideband show rich. Images below for examples. Should I trust the STFT histogram and just use those values for VE table modifications since its all part throttle tuning even though the wideband shows lean instead of rich?


ST Fuel Trims
Short Term.JPG

AFR Err/WideBand
AFR-WideBand.JPG

New Log attached

I am getting a P0103 now.



EDIT: I did some more research and it looks like before I really get into VE tuning I need to set the following.
I already have THe MAF Fail High set to 1Hz and COT disabled
Engine/Fuel/"Cutoff, DFCO"/Deceleration Fuel Cutoff/Enable ECT = 284
Engine/Fuel/"Cutoff, DFCO"/Deceleration Fuel Cutoff/Stall 12000rpm
Engine/Fuel/Power Enrich/Enable/Min Map = 75 instead of 55 just to keep me out of PE mode longer
Copy High Octane to Low Octane table since it looks like a failed MAF will force the ECU to use the Low Octane table

And then I need to Reset the Fuel Trims

My biggest question is why my STFT show rich and Wideband shows lean in the lower RPMs? Im going to guess that its because the Fuel Trims are doing the correcting and if I was going to tune with the Wideband O2 I would have to Disable both the STFT and the LTFTs again. Is that right?

[edcmat-l1]

I have MAF disabled but a question before I go and modify VE in the wrong direction. The STFT show rich just like the narrowband O2s show but the AFR Err table and Wideband show rich. Images below for examples. Should I trust the STFT histogram and just use those values for VE table modifications since its all part throttle tuning even though the wideband shows lean instead of rich?


ST Fuel Trims
Short Term.JPG

AFR Err/WideBand
AFR-WideBand.JPG

New Log attached

I am getting a P0103 now.



EDIT: I did some more research and it looks like before I really get into VE tuning I need to set the following.
I already have THe MAF Fail High set to 1Hz and COT disabled
Engine/Fuel/"Cutoff, DFCO"/Deceleration Fuel Cutoff/Enable ECT = 284
Engine/Fuel/"Cutoff, DFCO"/Deceleration Fuel Cutoff/Stall 12000rpm
Engine/Fuel/Power Enrich/Enable/Min Map = 75 instead of 55 just to keep me out of PE mode longer
Copy High Octane to Low Octane table since it looks like a failed MAF will force the ECU to use the Low Octane table

And then I need to Reset the Fuel Trims

My biggest question is why my STFT show rich and Wideband shows lean in the lower RPMs? Im going to guess that its because the Fuel Trims are doing the correcting and if I was going to tune with the Wideband O2 I would have to Disable both the STFT and the LTFTs again. Is that right?

Yeah you can disable all that if you want. Don't exactly have to if you know how to filter or just use the areas you need to.

Need to start using the correct terminology and get away from "STFT show rich" because they don't. They're pulling fuel. And they should be. It would be the O2 sensors that "show rich" and the fuel trims are reacting to that. A cam with overlap will reduce the volumetric efficiency of the engine in the lower RPMs especially idle and just off idle. So the correct reaction of the fuel trims is to pull the fuel back.

Your long terms still look like they're active in your last log. Need to disable them to use STFT only, or you can combine LTFT and STFT in your histogram. My preferred method is to disable the long terms.

As for your wideband, just ignore it at anything part throttle.

[joshlarsen]

Yeah you can disable all that if you want. Don't exactly have to if you know how to filter or just use the areas you need to.

Need to start using the correct terminology and get away from "STFT show rich" because they don't. They're pulling fuel. And they should be. It would be the O2 sensors that "show rich" and the fuel trims are reacting to that. A cam with overlap will reduce the volumetric efficiency of the engine in the lower RPMs especially idle and just off idle. So the correct reaction of the fuel trims is to pull the fuel back.

Your long terms still look like they're active in your last log. Need to disable them to use STFT only, or you can combine LTFT and STFT in your histogram. My preferred method is to disable the long terms.

As for your wideband, just ignore it at anything part throttle.

Thanks for all the info and help and your correct I was using the wrong terminology for the STFT being rich. I'll get LTFTs disabled and plan to do some work on tuning it this afternoon. I assume were using STFT because its quicker than trying to have the ECM learn all the LTFTs.

[edcmat-l1]

Thanks for all the info and help and your correct I was using the wrong terminology for the STFT being rich. I'll get LTFTs disabled and plan to do some work on tuning it this afternoon. I assume were using STFT because its quicker than trying to have the ECM learn all the LTFTs.

That's correct.

[TheMechanic]

Copy High Octane to Low Octane table since it looks like a failed MAF will force the ECU to use the Low Octane table

Personally I like to use the low octane table. I don't want any knock or any issues with timing to hinder my fueling changes. Once I have fueling good THEN I will start working on things like Idle and timing.

[joshlarsen]

Been busy so havent had a ton of time to work on tuning and I also was having issues with the trans getting to 250degree F so I added a standalone cooler which now keeps the trans temps below 160F. I also had some exhaust work done and decided It was best to get that finished before going too far with tuning. I have the VE tables pretty well dialed in with most cells between 0 and -2 for STFT. I have been trying to keep everything so it was not having to add fuel, figuring thats atleast on the safe side. I havent had any issue with stalling now and the cruise contolling issue is mosly gone and I'm pretty sure I can clean that up with in gear airflow. I havent done any long hard pulls so I'll have to come back but for normal daily driving its decent.

Im going to switch to tuning MAF now that VE is decent. Since Im still not doing long WOT pulls should I tune MAF using the STFT also or the way I had started tuning MAF back before I worked on VE was by disabling both STFT and LTFT and using my wideband?