Idle dip on small cam 13 Camaro STFT's MAX OUT

So you think this is "newer" update issue ?
I've been having this problem for a while now, after reflash with newer VCM version.

This is a HP Tuners issue. Any time you flash certain cars even if its stock it will start doing this. They need to fix there software so we dont have to tune around it. Been several years and still no fix.

1. Your base spark seems a little low in the idling range
2. Your final idle area table seems a little low
3. Your startup airflow looks a little low
4. Your MAF Calibration looks very rich
5. Turn your long term fuel trims back on

I don't think this is an HPT caused issue. I can't say that I have ever read a stock cal on stock car just to write it back with no changes just to see if the problem manifested, but I don't believe that is the case.

I have came to the conclusion that it is caused by a post catalyst 02 test that tries to run. It happens on most calibrations from 2012 on. The way to tell if your calibration will have the problem is to check Engine diagnostics / Exhaust / Oxygen Sensors / [ECM] 303 - Post O2 Test. If the stock calibration already has this set to disabled then it will have this problem. Prior to 2012 all factory calibrations will have this test set to enabled. Setting it to disabled stop the test from running. Ones that already have it disabled apparently still have the test turned on, but most likely they added a new test and it has a new switch that HPT have never added to their editor for us to disable.

The problem shows up when the post cat 02's are removed. The test runs when under deep deceleration, like coasting at 0 throttle and such. The STFT's peg at 30%+ and it dumps an extra amount of fuel. Normally the rear o2's see this change and react with increased voltage. Once it see's them react, it checks the test off its list and usually doesn't do it again. If the rear o2's are not present, they obviously can't change and it just keeps adding the max allowed STFT fuel until RPM or TPS moves out of the range for the test. This happens and keeps happening every time you let off the throttle for around 10 minutes, then it finally gives up and times out. Stock cams are usually pretty tolerant of the rich afr and often you wouldn't notice it happening unless your watching the STFT's. Any descent sized cam are will typically fall on its face and choke out and want to die when it adds that much fuel. Hard to miss for all those who claim to have never seen it. And 99% of post 2012 vehicles with no rear o2's sensors will exhibit this.

I have tried every combination of settings I could imagine would ever affect this and have not been able to stop it from happening. So far my only solution is to make sure they rear sensors stay in place even on a race car with cats removed, or to disable the front o2's because with all of the 02's off none of those test run.

I first noticed this problem back around 2013. I have seen a few observant people chime in about this on the forum, but they are usually met by the normal mob on here telling them they are "stupid" or "tune is wrong". The normal "I've tuned 1000's of cars and never seen that problem, go away the problem doesn't exist". I probably should have took the time to contribute before this, but trying to be constructive on this forum for the last 10 years is usually a waist of breath.

Go to the o2 sensors tab, and force it into the idle trim cells by setting the ltft idle mph to 317 and 318 or something. It prevents it from entering the decel fuel trim cells that must be required as a prerequisite to run this test. You still get decel/coastdown spark, just not the silly test we can't otherwise disable. (Credit goes to Steck on this one, if I recall correctly.)

Well what do you know, there is still some good on this forum! :cool:

Thank you for sharing and thanks to Dave for figuring it out. The last time I searched for information about this was many years ago. I had given up and just been dealing with it for the past 5 years. Is this something that would be common knowledge in some other thread if someone knew what to search for? I was remote tuning for a customer who needed a software update and the main website was down today. I just by chance checked to see if the forum was down also, and this was the top thread on the list and caught my eye. What luck, lol, as I venture to visit this forum once, maybe twice a year.

Here's one I posted at some point:
https://forum.hptuners.com/showthrea...78-STFT-Issues

Here one where Dave put it out there (assuming he gets the credit... he's the only one I've seen post about it. I just mention it when it comes up again):
https://forum.hptuners.com/showthrea...-high-on-decel

Good to see you posting, by the way!

Thank you again. Maybe this has enough stuff worded differently that more people will find the answer to this problem during a search. The links you provided should shed light for anyone having this issue.

Crossing forum sections, but have any of you guy's run into this on a gen V di platform? Having this same issue on my heads, cam, headers, no-cats 17' SS 1LE. After a DFCO decel when the injectors come back on the STFT goes to 27% and I get a dip then a flare in rpm. If you just push the clutch in without a decel first the STFT are around zero and the rpm will drop normally and catch at 1000 rpm. Obviously the VTT and VVE are tuned and the car runs well otherwise. My rear o2's are in place, have all the response codes and post catalyst fuel codes shut off. I tried this trick with the LTFT idle with no luck. More tables or drop down tabs we need added?