Rich or lean?
Former Vendor
Joined: Dec 2016
Posts: 3,574
Likes: 2,412
From: Lookin over Hoover Dam
Ok, well that likely eliminates that is has a tune on it, because most people who throw a mail order on there, will disable cags. Seems the likelihood is that the elevation your running isn't allowing the motor to pull enough vacuum in decel to trigger the deceleration fuel cutoff at the rpms you're decel from. A tune would definitely eliminate it more, by modifying the decel fuel cutoff MAP entry and exit tables. Someone could do it through a mail order tune, dump the cags for you and tweak a little. Just be sure to tell them exactly what you want. The PCM is in the right wheel well behind the little panel. Sometimes they're a B to get out if they've been in there a little while. My plastic mount broke on mine, and I had to replace it (cheap online to buy).
Overall though, without a tune, there won't be much you can do. Ideally if you could find a capable HPTuner or EFILive guy in your area, they could address it directly, and/or do a scan. Once you go into decel, no pops and bangs are possible because fuel shuts off entirely but obviously as the car gets close to idle rpm, it needs to re-enable the injectors to run...so there is an entry and exit parameter.
It comes down to if you can tolerate it or not I suppose. I personally tuned mine to shoot fire on decel and scare off the Mustangs behind me.
Overall though, without a tune, there won't be much you can do. Ideally if you could find a capable HPTuner or EFILive guy in your area, they could address it directly, and/or do a scan. Once you go into decel, no pops and bangs are possible because fuel shuts off entirely but obviously as the car gets close to idle rpm, it needs to re-enable the injectors to run...so there is an entry and exit parameter.
It comes down to if you can tolerate it or not I suppose. I personally tuned mine to shoot fire on decel and scare off the Mustangs behind me.
Last edited by KnightDriveTV; Apr 23, 2019 at 08:51 PM.
Burning Brakes
Joined: Feb 2006
Posts: 983
Likes: 364
From: Stafford Virginia
Melting Slicks
Joined: Feb 2001
Posts: 2,803
Likes: 357
From: Northville, MI
This is from years ago by one of the engineers who developed the C5 software beginning in 1992, from what they said I believe it is the "Dual Cone Aircleaner"
In designing the C5 GM engineering did a ton of testing and from that wrote adaptive strategy (A.S.) that made assumptions as to air and fuel flow under different engine conditions.
Changing those airflow parts, especially larger ones, reduce the velocity and the A.S still functions as if the stock parts were being used and how it was programmed and does not change even with tuning.
Most cases when the gas pedal is lifted and goes into “decel” with the larger airflow parts confuses the PCM and is adding or removing fuel when it really did not have to.
In designing the C5 GM engineering did a ton of testing and from that wrote adaptive strategy (A.S.) that made assumptions as to air and fuel flow under different engine conditions.
Changing those airflow parts, especially larger ones, reduce the velocity and the A.S still functions as if the stock parts were being used and how it was programmed and does not change even with tuning.
Most cases when the gas pedal is lifted and goes into “decel” with the larger airflow parts confuses the PCM and is adding or removing fuel when it really did not have to.
