Rough running at or slightly above idle. Any ideas?

[Bossy1908]

I've had my Boss since last November, have around 2300 miles on it, and have had this issue from day one. When at idle, the engine appears to stumble slightly. It almost feels like a miss. You can feel a slight stumble and even hear a small "pop" from the side pipe. Sometimes I'll even get an occasional backfire from the side pipes on decel or downshift. I really do mean a backfire, and not that awesome snarl/braaap sound that we get on the overun. The baffles have been removed, but, like I said, this has been happening since I got the car. The car is bone stock-no trackey/intake/exhaust/tune or anything. A week after I took delivery I took the car back to a dealer that claims to have scanned the ecu for trouble codes. I was told there were none, and that without a "check engine" light, they didn't think anything was wrong. I was also told that these engines idle a bit rough and that is what I am probably feeling. I'm finding this pretty hard to believe as you can also feel hesitation or resistance when you are in neutral, just slowly raising the rpm up. It seems to shutter/stumble most noticebly in the 1500-2000 rpm range. After that, I imagine the higher revs are just making it less noticeable. I haven't had the opportunity to listen to, or drive, another Boss so I really can't say for sure that this is NOT normal. I just can't imagine that this is normal, especially since I haven't seen anyone else mention this here. I plan on getting the oil changed in the next week or so. Anyone have any ideas on what this might be, or what I can ask the dealer to do?

 

[SVT1]

Mine does it to.

It's not a problem. I don't like it but it doesn't affect anything at all. As long as there are No check engine lights, it is most likely fine.

I think the stock tune leaves something to be desired honestly, but then again, it is a 444 HP N/A 302 so overall i guess we have it pretty good when we can complain about stuff like this!

 

[BossTXB]

Mine does it too. A very rough and missing type idle between those RPMs. Seems like maybe an air/fuel thing? Does it do it with Track Key? I will have to try mine with Track Key sometime and see...

 

[302BOB]

My Boss idles very smooth with no popping or stumbling at all & never has from day one. Without an error code the dealer will assume everything is fine with your cars even though that may be not the case.

 

[legof16]

I'm not sure what it is either. My new Boss idles perfectly, but my 2012 Mustang GT started doing the exact same thing around 2000 miles. At first I thought that I may have gotten some bad gas as I was on my first road trip and got caught low on gas in the middle of nowhere and had to get QT 91 octane where I normally got it at a Shell or Chevron. It started the very next day. I took it to the dealership and got the standard, "This is how these cars are supposed to idle". For me, all I can say is that fortunately, it did lessen over time. By the time I sold it to get my Boss, (a few weeks ago), it was idling near normal. I was the only one that could notice that it was still idling a little rough; my friends and even my wife thought I was acting paranoid. I did notice that using the highest octane gas you can get did seem to help a little (add couple oz of torco).

Cheers
Lego
2012 Stock Performance White Boss #2351

 

[Bossy1908]

Mine does it to.

It's not a problem. I don't like it but it doesn't affect anything at all. As long as there are No check engine lights, it is most likely fine.

I think the stock tune leaves something to be desired honestly, but then again, it is a 444 HP N/A 302 so overall i guess we have it pretty good when we can complain about stuff like this!

I guess if some of us have this issue, and some of us don't, then there is something not 100% right with my car. All I can hope for is that the next tech that works on my car has enough skill to troubleshoot the issue beyond the diag scan. Again, any info from anyone on this is much appreciated. :-\