Just had a Magnaflow muffler installed with new, stock exhaust pipes and tips on my 91 TA (305 TPI single exhaust). Cat was replaced with an OEM a few years ago and everything forward of that is original stock.

System sounds great when accellerating or just cruising at steady speed but pops loudly whenever I downshift and let the engine brake the car.

Has anyone else experienced this and what can be done to eliminate it? My driving style wont change to reduce the number of downshifts and I hate to roll up to a light with a bang.

Any advice would be appreciated.

 

Bump. Any help or reason for the "backfire" I am getting with the new muff?

 

im no expert but i think that may be a sign of excess fuel.

 

Thanks. But why would it only show up after the muffler and pipes were changed? I'll check ignition components but unless the computer is reacting differently to the dif exhaust components, nothing else has changed. Appreciate the thought.

 

magnaflow mufflers are straight through, so if the engine is popping, the magnaflow won't muffle it like others will. To be honest it sounds to me like you are engine braking an excessive amount.

 

Thanks for the input, but my magnaflow is an OE single exhaust replacement (1 input; 2 output) not a straight thru. Engine braking is not excessive, the pops occur even if I do not downshift and slow down in 5th from normal road speed. They are just more obvious going down a gear but I keep the RPMs below 3500 when doing so. Just rolling up to a red light at 20 MPH in 2nd will cause it to pop. I have owned this car for almost 20 years and it has never done this. I plan to look into ignition causes (plugs, wires, dist cap, rotor, etc.) if no one has an explanation based on the pipe/muffler swap.

 

Yes magnaflows are straight through, thats what a magnaflow is, that is their claimed benefit. I know you have a stock type muffler but the baffling and sound deadening is a straight tube, there are not baffles that obstruct the flow of the exhaust like other mufflers. If your car majically starting poping like this after you put the muffler is on and nothing has changed then I'd guess the car/your driving style has always done it and now you have a muffler with no baffles and it's not deadening the poping pulses.

 

I agree with the suggestion that maybe you have too much fuel, sounds like it is back firing a little. Maybe your engine is running a little bit rich? Just an idea. My camaro is carbureted and I also just had a magnaflow installed and am having the same issues, popping and backfiring when I let off the throttle or when I down shift. I messed with my carburetor and was able to get it leaned out some, now it runs so much better, more power not to mention the popping and backfiring is all but gone. Hope you get it figured out buddy (:

 

I appreciate the input. Mine is a TPI car, but the thought is the same. I plan to investigate ignition, fuel, and airflow causes in the next few weeks to see if I can effectively do the same thing you did with adjusting your carb. Glad to hear yours is running better after the adjustments. It might be that the ECM needs to adjust the mixture and maybe all I need to do is drive it more so it "learns" the new operating parameters.