RPMs surging when decelerating

[aharrel9]

I recently cut my muffler off and ran true duals under my 2015 Ram 1500. Now when I am going down a hill at slower speeds, 35-40 mph for example, my RPMs will go up and then fall back down as I come to a stop. Do I need to be concerned with this? Is there a way to fix this? Please any input would be great!

 

[U&A]

Are you sure the transmission is just not doing its job and trying to do a little bit of engine braking to help slow you down.....?

My truck does it all the time and it supposed to. it does it a lot more especially in tow haul mode.


Sent while firmly grasping my redline lubed RAM [emoji231]

 

[Burla]

You have straight pipes? If so no back pressure, you might want to put a muffler or glass pack back. Scaveging.

 

[U&A]

Generally speaking today’s vehicles have such restrictive catalytic converter‘s that if you leave the cat on and do a straight pipes after the cat you’re not going to hurt anything. You’re also not going to help anything either unless you have a tune for it.


Sent while firmly grasping my redline lubed RAM [emoji231]

 

[Burla]

Yeah, but did he cut those off too? just need more info. define true duals.

 

[RAM DRVR]

Sounds like engine braking to me. Transmission downshifts which increases RPM's.

 

[RoadRamblerNJ]

Sounds like engine braking to me. Transmission downshifts which increases RPM's.

Nope, not engine braking.
It happened to me in my '09 1500 5.7
Damn thing, while coming to a stop or just sitting still would sometimes just surge up & down, up & down from a very low 500 rpm to 1500 rpm and back down. I took a video of it. Still trying to locate that. I'll post it if I can find it.

 

[U&A]

get your PCM scanned and flashed.

That will give you some answers


Sent while firmly grasping my redline lubed RAM [emoji231]

 

[tidefan1967]

I agree with Burla. If you completely straight piped it (no cats or mufflers) its basically in limp mode because it has no idea how to adjust to the lack of back pressure with the factory computer. I had the same thing happen to my 95 Dakota with the Magnum 318 back in the day. I went from the factory single exhaust to true duals with no cats (I went with dual Flowmasters because thats what we all ran back in the 90's) It ran like **** no matter what I did. The only thing that helped a little was premium fuel. More than likely if you get a custom tune that will fix the problem. Needless to say that's the last time I tried to fix **** that wasn't broken.

 

[corneileous]

Generally speaking today’s vehicles have such restrictive catalytic converter‘s that if you leave the cat on and do a straight pipes after the cat you’re not going to hurt anything. You’re also not going to help anything either unless you have a tune for it.


Sent while firmly grasping my redline lubed RAM [emoji231]

I was told by a muffler shop that Ram only uses high-flow cats...


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[corneileous]

I agree with Burla. If you completely straight piped it (no cats or mufflers) its basically in limp mode because it has no idea how to adjust to the lack of back pressure with the factory computer. I had the same thing happen to my 95 Dakota with the Magnum 318 back in the day. I went from the factory single exhaust to true duals with no cats (I went with dual Flowmasters because thats what we all ran back in the 90's) It ran like **** no matter what I did. The only thing that helped a little was premium fuel. More than likely if you get a custom tune that will fix the problem. Needless to say that's the last time I tried to fix **** that wasn't broken.

I was under the impression today’s vehicles need to have an X pipe or H pipe whenever true duals were ran with no mufflers in order to get any kind of benefit out of it or at least keep it from running worse. I was never interested in true duals, I was happy with just catback. I figured the only people that ran true duals was those who had a hot cam installed, high-flow heads, headers, performance tune, forced air.


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[tidefan1967]

I was under the impression today’s vehicles need to have an X pipe or H pipe whenever true duals were ran with no mufflers in order to get any kind of benefit out of it or at least keep it from running worse. I was never interested in true duals, I was happy with just catback. I figured the only people that ran true duals was those who had a hot cam installed, high-flow heads, headers, performance tune, forced air.


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Most post 1996 vehicles(OBD II) are going to run like **** without the cats because the ECM knows that they've been removed and it basically is not made to compensate for such a big change in performance. A custom tune should fix the issue but nothing else will.
Hell I used to get the cats cut off my vehicles and have duals installed. Most pre 96 OBD I vehicles could adjust to the change whereas anything after that could not. I eventually grew out of it and quit throwing money down that hole. Nothing wrong with a catback system but I'm happy with the way the factory exhaust sounds.

 

[corneileous]

Most post 1996 vehicles(OBD II) are going to run like **** without the cats because the ECM knows that they've been removed and it basically is not made to compensate for such a big change in performance. A custom tune should fix the issue but nothing else will.
Hell I used to get the cats cut off my vehicles and have duals installed. Most pre 96 OBD I vehicles could adjust to the change whereas anything after that could not. I eventually grew out of it and quit throwing money down that hole. Nothing wrong with a catback system but I'm happy with the way the factory exhaust sounds.

I remember back in the day they made those dummy O2 sensors that was really nothing more than just basically a microchip that gave the computer the same reading as an actual O2 sensor that was reporting a normally functioning cat.


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[StoneDude76]

Do you have the 8speed? If so its normal.

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