Ok I cant get a for sure answer ot this ? and I have used the search option and still cant! I have a 03' ECSB 4.8 mods in sig. The exhaust is Flowmaster 50 series catback single in dual out and although I am going to be changing in near future I need to know whats up now. Say I hit 80 mph and just let of the gas,take my foot of the pedal and let it just wind down. My exhaust will start crackling and popping for about 3-4 seconds and then quit and then 1000 or so rpms later it will do the same thing. This only happens if I go over like 50. What the hell is this,can it be fixed and is it hurting anything. Ive heard exhaust leak,running rich,burning excess fuel and other sh*t. Help me out!

 

With my magnaflows I was told by three shops and two people it was absolutely normal for a free flowing muffler (but this doesnt explain the flowmasters doing it). Mine does the same thing.

 

Running rich is usually the culprate, but that's usually on carbed engines(rare on EFI). However, smell your exhaust and see if it's rich. Pops or crackles can also come from improper scaveging of exhaust gases (such as true duals without H/X-pipes on low HP motors). So, an exhaust leak could be it. Are the Slowmasters welded or clamped on? You may want to check those for leaks. Another reason could be the timing is off a tad, however, this is usually on distributor based engines, and I know it's near impossible to have offset timing on direct fire engines. So, just check for leaks, that's probably the culprit.
Philip S.

 

My exhaust is all welded! The thing is that it just started doing this about a month ago and Ive had the exhaust for 8 months. It was doing it before I just recently got 4.10 gears and a updated tune for the 4.10's. It seemed to get alot worse after I did the gear swap!

 

My magnaflow does the same thing and I'd say it's normal and related to backpessure but can't give you a technical reason why. I kind like it.

David

 

My flows do it but my dad's on his ford does not.

 

I had an 84 chevy with a 350 and 40 series and my truck did the same thing. First time it did it was because i had a vacum leak and as soon as i foudn it the problem was fixed. then a couple months later it started back up, of coarse the first thing i tought was vacum leak. I searched for months replacing pretty much every vacum line on teh truck. and on those old triucks that is alot of vacum lines. well to make a long sotry short my dad and i were messing around and it ended up being the Rochester Carb. jet screws started unscreawing from vibratiions making it run rich. we adjusted it to were it was running better and gave it a tune up and solved everything. After that it ran a ton better and saved on gas. but as he said ef egines should run rich but if your messing with teh programming of teh computer you never know.

 

Does your truck have air injection on it, if air is getting into the exhaust when you let off the gas it will do this. Some crackle is normal for a free flowing muffler (Isn't a crackally exhaust the whole reason for an aftermarket exhaust) My truck did it nicely when it was stock with only the Flowmaster 40 series delta flow, when I had a cam in my 5.3 the crackle went away ,now with headers and the 6.0L, it sound nice again.
But if it is explosively poping with a 50 series then I would say air is getting into the exhaust system near the front.

 

it does that because of back pressure the motor doesn't have enough compression to not do that but it won't hurt anything it's just from the low compression stock motors make. by the way your exaust is dumped i guess

 

Thats cuz with deeper gears you can just let off of the gas and start slowing down pretty quickly, when the motor revs down, the exhaust will pop, mine does. When you brake, you don't really notice it because the rpms drop much quicker.