Hey guys/gals,
I just installed a flowmaster american thunder kit on my truck. It's an 05 FX4 Scab with the 5.4L. The install was incredibly easy, except the hanger bracket for the driver side.

Any ways, Now that it is on, I love it. SOunds awesome. But every now and then when I get in it and start it up, I give it a nice little rev, and it barks really bad. Meaning the rev down, I get like a backfire tin canny sound. REALLY LOUD. I would say it's a back preasure issue, but it is only right after I start for about 5 minutes, then I can rev my heart away. I can even run the truck for a while, then shut it off, restart and it does it again. So it isn't a hot/cold issue.

Any ideas? It's really REALLY annoying.

 

called flowmaster tech support and he had no idea. Said they haven't had any cases of this. I'm have wondering if it is because the truck has 200 miles on it. Something with an engine learn process maybe?? so confused, and so afraid to rev it. haha. sucks

 

i say drive it some more.. then see if it still does it.. The computer may need time to adjust and learn, since you did use put on a much more free flowing exhaust system compared to the stock one.

 

what do you think is causing it? Lack of back preasure? Engine breaking in? It does seem to do it less and less. So Hopefully soon it just goes away. I'd like to rev it when it people ask me about the exhaust.

 

do you think that unplugging the battery for 5 minutes and resetting the ECU would do anything to help anything?

 

My Magnaflow system did the same thing when I first put it on. After some driving and letting the computer relearn it is fine.

 

ok. I let it go for a while. I did notice that when I have some else rev it, I can see a subtle stream of black smoke shot out of the tailpipes, when it is making that popping noise. Only a small amount, but still noticeable that it is pure black.

I'm thinking it's just the engine learning too, we'll see I guess.

 

sounds like what my ' 87 5.0 mustang has done since new and i put flowmasters on only does it when you first start it up,i changed to dynomax(everyone has flowmasters)and it still does the same thing.personally love the sound,my '98 expedition does the same thing 5.4 w/dynomax ultra flow