2016 Weird Throttle speed wont drop down when driving

[englishrodder]

Hi All, New VOA member here that just joined.
I have a 2016 ACR-E that was purchased last year with only 4 miles on it, did the proper run in. About a month ago i added a full Bellanger headers, 2.5" system with Cats, DSE Smooth tubes and K&N Panel Filter with a HP Tune.
When the car is not under load the engine revs and runs great.

Weirdly this just started, when driving and slowing down to a stop she will remain at about 1500rpm, then drop down to tick-over maybe 2-5 seconds later (Set at 700rpm), (Its almost as if the same effect on a carbed car when a return spring isnt strong enough).
I swapped back to the stock tune to see if that fixed the issue....it didn't.

I checked all intake connections, tubes etc
I haven't taken it into the dealer to do a throttle relearn (Don't know if i should do this...)

Car has about 2200 miles on it now
Any ideas where i should start looking at?
Thanks

[englishrodder]

Anybody?
I swapped out the O2 sensors again on both sides, made sure no exhaust leaks, no intake leaks and the PCV plugged (Im using Doug Shelby catch cans to atmosphere).

Guess im gonna have to take it to a dealer for diagnostics

[CNU_Physics]

I don't really have anything to help you with, but from what I understand with HPTuners you should be able to do the throttle relearn with it, no need to go to the dealership. It would be worth a try to get that done.

[CarbonDan]

Definitely sounds like a good candidate for a throttle relearn.
Assuming absolutely no possibility of actually physically hanging on the throttle (floor mat, clumsy foot placement etc), it sounds very much like a question for the tuner.

[Arizona Vipers]

This is 100% a throttle relearn issue. When you did the tune, did you take to the dealer for the throttle relearn? If not, you need to.
Scot at Prefix did mention to me that there might be a way to do it in the future with HP Tuners, maybe you can now.

[Steve M]

You can do the throttle relearn with HPTuners...have been able to for years (5+ at this point).

But there's a catch: you have to own the interface. If you got a tune through a shop that used their interface to license your PCM, then only they'll be able to do it.

[englishrodder]

Thanks all, Will try if i can do it via the HPTuner suite. If not will swing by the dealer.

[Steve M]

The functionality resides in the HPT Scanner software. Connect to the vehicle, and then look for something along the lines of "special functions". It'll walk you through a series of pop-ups that will accomplish the relearn.

[usmcfieldmp]

This thread has a discussion on when they requested and implemented the relearn into HPT.

Posts 36 & 37 specifically. Early days of a beta, but the process should be similar.

https://forum.hptuners.com/showthread.php?53109-Gen-4-(2008-2010)-Viper-Issues-Requests

[englishrodder]

Thanks all for the info, and thanks USMCFIELDMP for that link - useful info
It appears that HPT has removed the Throttle Relearn procedure from the VCM Scanner (And Editor) as when it loads its just blank.... Guess its time to go to the dealer... The one near me are idiots..wanted to book me in for something thats 10mins but said they need to allocate 2hrs...Thus its 5 weeks out !

Thanks all - gonna take her to a dealer with a Viper tech that has been reccomended
47954

[Steve M]

Based on that screen shot, it doesn't look like the scanner is connected to the vehicle.

Turn the car to the ON position (but don't start it), and connect your HPT interface to the OBD-II port. Wait about a minute, and then click on the "connect" icon. If it connects properly, all of the parameters should start showing values. If some are still greyed out, hit the disconnect icon and then reconnect. At some point, it will be communicating properly with the PCM; at that point, then try the controls and special functions icon and see what it says then.

It won't show anything until you connect to the vehicle due to how the scanner works - it polls the vehicle to figure out what it is, and then looks up what is supported before displaying it to you.

Edit: so it'll only start showing values if you start recording, but if you are seeing greyed out parameters, it likely isn't properly connected to the vehicle.

Sometimes it takes 2-3 attempts on mine before the parameters show up correctly in the table.

[englishrodder]

Based on that screen shot, it doesn't look like the scanner is connected to the vehicle.

Turn the car to the ON position (but don't start it), and connect your HPT interface to the OBD-II port. Wait about a minute, and then click on the "connect" icon. If it connects properly, all of the parameters should start showing values. If some are still greyed out, hit the disconnect icon and then reconnect. At some point, it will be communicating properly with the PCM; at that point, then try the controls and special functions icon and see what it says then.

It won't show anything until you connect to the vehicle due to how the scanner works - it polls the vehicle to figure out what it is, and then looks up what is supported before displaying it to you.

Thanks - weird it said it was connected maybe i did it too soon and the PCM wasnt fully initialized etc... will try again tonight when i get home

[Steve M]

I edited my statement above about being properly connected.

The PCM in the Gen 4/5 Vipers is pretty chatty when you first turn to vehicle to the ON position - that's why it can take about a minute or so before it finally shuts up and is ready to listen to the HPT interface.

It's just one of those quirky things, but definitely give it a couple more shots before you throw in the towel. There is a possibility they never enabled the throttle relearn for the Gen 5 crowd, but I don't see why they couldn't, because it certainly is included and works for the Gen 4, which is nearly identical PCM-wise from what I can tell.

If it truly isn't there, it would be worth sending an email to HPT support to see if they might be able to add it in beta for you.

[englishrodder]

Thanks for all the help, after a few tries with the WiTech at the dealership we got her running all good again and with proper throttle response. :smileys-car-driving