Desired Idle RPMs = 0... Until System Check Complete

[LaTechGTO]

I've searched the internet far and wide only to arrive at open-ended threads with no resolution or description so I thought I would post my findings. What started all of this was that I was experiencing was a sluggish idle until after about 6-10 seconds of sub-target RPMs, and I previously had my RAF tuned where it was right on the money then I added a little bit of extra airflow to allow my STITs to be slightly negative. I added a little extra RAF for this experiment to see if it would help so you will see my STIT might be a little more negative in the logs than they were previously.

After doing a few start-up scans and looking at the logs, I started altering the Start-up and Friction Airflow values, hoping I would see some correlation to when the car would hit the target idle RPMs. I noticed the RPM corrections didn't seem to occur until well after the Idle PID loop is to be enabled (4.5 sec if no flares occur) - I originally thought this was taking control. In some cases the time would be different than others... this temporarily stumped me.

Before starting the car, I could connect to the car with the scanner, command 800 RPMs, cycle the key quickly to build fuel pressure (not losing the connection), turn the key, and the engine would start PERFECTLY, coming right up to idle. I finally decided to pay closer attention to the Desired Idle RPMs, which I should have done from the beginning. Viola! I watched the gauge cluster in the car instead of the laptop screen, and I noticed the RPMs didn't correct until the "System Check" was completed. Sure enough, the Idle Desired RPMs cell remains zero until the system check occurs and then slowly rises incrementally until it reaches the desired RPM.

So that solves the mystery... how to correct it? Some of you may wonder why I care and would suggest that I just wait until the system check is completed to start the car. Well, here is the caveat - I am running a return style fuel system so the fuel pressure builds on the initial key-on then returns to zero shortly afterwards. The car will still start and come right up to idle if I let the system check complete, but there is delay in the engine firing up because fuel pressure has to build some before starting. Back when the car was stock or HCI, I am pretty sure I could turn the key forward, without waiting for the system check to complete, and it would go straight to the correct idle RPMs.

Do I just increase my Start-up and Friction Airflows? I adjusted these some yesterday (and last week) and didn't notice a big difference, if any at all, but I also didn't max them out to see. What is the correct way to achieve this without waiting for the system check to complete? Haha. The one good thing about starting the car before the system check is that it will be consistent timing from key-on since it always happens at nearly the exact time, every time. Ex. Key-on > 1 sec, 2, sec > Start

Logs and Configuration attached for reference.

IDLE-Airflow.cfg
Idle Try 1.hpl
Idle Try 2 - 800rpms Commanded.hpl
Idle Try 3.hpl
Idle Try 4 - and SOLVED.hpl

Hopefully this will help someone else who's running across the same issue!

[LaTechGTO]

Just curious if anyone figured out how to work around this issue or not. It sure would be nice to be able to start my car while fuel pressure is at it's set point.

[GregRexAdams]

I have a car doing this. It is an auto swap car with a 58 to 24 converter box. If put it gear, desired goes to normal. It pulls timing to bring idle speed down. I haven't found a fix yet.

[LaTechGTO]

I have a car doing this. It is an auto swap car with a 58 to 24 converter box. If put it gear, desired goes to normal. It pulls timing to bring idle speed down. I haven't found a fix yet.

That is odd... mine is a little different than that, but it would be nice to find out what I could do to make the desired RPM to pull from the ECU (or go to a default - not "0") from the get-go instead of having to wait for the system check to complete.

[Lakegoat]

I don't have that particular problem, but I changed the fuel pump prime time to 6 seconds so I don't have to worry about starting in 2 seconds. '05 GTO, return fuel system. Post up your tune.

[Lakegoat]

I don't have that particular problem, but I changed the fuel pump prime time to 6 seconds so I don't have to worry about starting in 2 seconds. '05 GTO, return fuel system. Post up your tune and modifications.

[LaTechGTO]

I don't have that particular problem, but I changed the fuel pump prime time to 6 seconds so I don't have to worry about starting in 2 seconds. '05 GTO, return fuel system. Post up your tune and modifications.

Ahhhh I didn't realize I could change the length of time the pump primed. I started to setup a toggle switch for a secondary fuel pump signal to trigger the relay to get past this issue. Great job figuring that out!

I'll have to post my tune later as I am at work and don't have it on-hand. 2004 GTO setup includes a 402ci w/F-1A, 4L80E (swapped from M6), Meth, FlexFuel (not running the correct OS yet since I still need to perform a full auto tune swap with a TechII; trying to keep from buying credits twice in case the VCM ID changes), etc.

[MikeOD]

I think that's your problem right there...2004 GTO M6 base code...my buddy ran into the desired RPM = 0 thing too, was a giant PITA at first due to the PRNDL wiring he had to add. HPTuners gives us access to the desired Idle RPM in gear and in park neutral with AC on and AC off...but they don't give us access to the mad idle RPM parameter in gear and in park/neutral...in the 2004 GTO M6 OS, it's set to 1200 RPM in gear, and 0 RPM in park. In the A4 OS it's set to 1200 RPM in both. EFILive has the parameter...maybe HPTuners can add it if you request it from support.

Download the EFILive demo, then download the GTO M6 and A4 tunes from tunefiledepot and you can see the difference. The setting in question is B4602.

[MikeOD]

...the same setting is set the same way in manual transmission Silverado's, the 2004/2005 CTS-V and 4th gen F-Bodies as well...so without a reflash to an auto base file, they have similar annoying idle issues when swapped to an auto without a base OS re-flash.

I believe you can log the PRNDL status in the scanner and see what's going on.

[LaTechGTO]

I think that's your problem right there...2004 GTO M6 base code...my buddy ran into the desired RPM = 0 thing too, was a giant PITA at first due to the PRNDL wiring he had to add. HPTuners gives us access to the desired Idle RPM in gear and in park neutral with AC on and AC off...but they don't give us access to the mad idle RPM parameter in gear and in park/neutral...in the 2004 GTO M6 OS, it's set to 1200 RPM in gear, and 0 RPM in park. In the A4 OS it's set to 1200 RPM in both. EFILive has the parameter...maybe HPTuners can add it if you request it from support.

Download the EFILive demo, then download the GTO M6 and A4 tunes from tunefiledepot and you can see the difference. The setting in question is B4602.

Thanks for the information and confirming my suspicion! I never had an issue or noticed the commanded idle RPM (no need to log it) when I was a M6. I had a feeling my ECM and PIM weren't talking because I have wired up my PRNDL from day one, and it doesn't seem to be sending a signal anywhere - hence me trying to scan with a stock auto file then go from there. FWIW, my gear position PID for forward gears works correctly as the car shifts, but that doesn't really have anything to do with the shifter position. I have tried setting the PRNDL in the tune all 3 options I think there is a 1) Off 2) PRNDL and 3) PN (I could be mistaken), and none seemed to matter. This might sound dumb, but what is the "mad" in "mad idle RPM"?

...the same setting is set the same way in manual transmission Silverado's, the 2004/2005 CTS-V and 4th gen F-Bodies as well...so without a reflash to an auto base file, they have similar annoying idle issues when swapped to an auto without a base OS re-flash.

I believe you can log the PRNDL status in the scanner and see what's going on.

Thanks again for the tips and info!!!

[LaTechGTO]

FYI - I figured this was one of the many issues with not starting with a factory OS through a TechII. Now I am curious as to what else might be out there...

[Lakegoat]

I had a M6 car also, and have a 4l80. I sent my computer off and had an auto os put in and used a wiring harness and T42 from an auto car. I used the plug in wiring harness with 2 relays from PCM of NC instead of swapping the pins in the plug. Everything works. You don't use the ISS plug on the 80 trans, only the VSS on the far end with this setup.

I guess if you are manually shifting, you don't need this.

[LaTechGTO]

I had a M6 car also, and have a 4l80. I sent my computer off and had an auto os put in and used a wiring harness and T42 from an auto car. I used the plug in wiring harness with 2 relays from PCM of NC instead of swapping the pins in the plug. Everything works. You don't use the ISS plug on the 80 trans, only the VSS on the far end with this setup.

I guess if you are manually shifting, you don't need this.

Yeah, it's pretty simple for you 05/06 guys, and that harness with the relays isn't even necessary any longer since you have the ability to change transmissions in the tune (unless you are using the PWM and TCC On/Off). Before that was available, the harness with the relays was the only option; I actually modified my harness with the relays and such, thinking I wanted to control the TCC On/Off with the PWM signal, and by the time I got ready to start it up, I found out that someone found out how to run a different OS that was compatible with my computer and allowed a segment swap with a 4L80E. Kind of glad I didn't... I like the way it feels when it shifts now and couldn't imagine it being any softer. At the end of the day... All of that soldering on my back underneath the car for nothing! HAHA! The pin swapping in the ECU is still necessary in the 05/06 (and 04s), but that part of the job is SUPER easy. compared to soldering those micro-relays in a PCB.

I thought everything worked on mine until this little idle quirk. Oh well, I will have to get everything loaded with a TechII and then swap over to my FF tune. Did you reflash your cluster to an automatic version? I'm going to do mine as soon as I get my cable back that I let a friend borrow... IF the TechII doesn't do it for me when I reflash everything.

Yeah, I am only using the VSS (rear), but I would eventually like to get the ISS to work correctly to keep an eye on slipping clutches and such by comparing the ISS to the VSS. That would help differentiate between torque converter slip and clutch slip when comparing those with engine RPMs. Probably not necessary, but it would still be nice to have.

You're right - none of that is necessary if manual shifting. Kill the codes and use a P-n-P box to control the solenoid release/apply. I started to go that route for simplicity sake, but I am soooo glad I didn't now.

I've attached my latest tune you requested. Also, where does one go about adjusting the period in which the fuel pump primes?

V1.4 3 Bar.hpt

Thanks!

[Lakegoat]

Fuel System--Fuel Pressure---Prime Time
I have the Clustermod program and cable but did not set the dash to read the auto trans position. Just didn't need it.
When I first received the auto tune, it was not correct and I used the Clustermod to adjust speedo pulses in the dash until I figured out that wasn't the problem.
Hope you get the problem fixed.

[LaTechGTO]

Fuel System--Fuel Pressure---Prime Time
I have the Clustermod program and cable but did not set the dash to read the auto trans position. Just didn't need it.
When I first received the auto tune, it was not correct and I used the Clustermod to adjust speedo pulses in the dash until I figured out that wasn't the problem.
Hope you get the problem fixed.

Thanks for the information. I will have to give my tune a look and see if I can adjust that. Never noticed that entry before, but I've also never known to look for it.

Good deal. I was going to offer it to you, but since you already have it there is no need. I only plan to use it until I stop being lazy and fix the light inside the shifter. It is tough to see the selector position at night so I could really make use of the gear display in the dash.

What ended up being your issue with the speedo pulses needing to be modified in the cluster? I think I recall someone that did the swap and had similar issues to you... maybe YOU were the person in the threads I was reading on LS1TECH or LS1GTO

Thanks - I'm pretty confident that reflashing the ECU and PIM should resolve everything.

[LaTechGTO]

Fuel System--Fuel Pressure---Prime Time
I have the Clustermod program and cable but did not set the dash to read the auto trans position. Just didn't need it.
When I first received the auto tune, it was not correct and I used the Clustermod to adjust speedo pulses in the dash until I figured out that wasn't the problem.
Hope you get the problem fixed.

Yeah, I definitely don't have that option in my tune. "Fuel System" is very limited and only contains "General". I'm not even sure if the settings I see in there (Fuel Tank/Gauge) are used to communicate with the cluster.

[MikeOD]

This might sound dumb, but what is the "mad" in "mad idle RPM"?

It was a typo...I meant max idle rpm...the x is close to the d on the keyboard.

[LaTechGTO]

It was a typo...I meant max idle rpm...the x is close to the d on the keyboard.

Ahhhhh that makes sense. Sorry, I live in a world of acronyms at work and on the internet so it's getting harder and harder to tell what's an acronym and what is a typo. I promise I wasn't trying to be disrespectful. Thanks for clarifying!

[LaTechGTO]

Fixed here: https://forum.hptuners.com/showthrea...cally-Changing