New exhaust backfires and bad cats

**xzaero0** · 05-20-2007, 09:16 PM

I have a 2000 TA A4 (not ws6) with edelbrock ceramic headers no cats and true dual exhaust 2.25 inch pipes and 02 sims. The car backfires at idol and after down shifting. Other than aftermarket hood, lid, filter and plugs its stock. There is no SES light but its annoying. I havent had it tuned yet, going to get it dynotuned soon, will this get rid of my backfires? Also I have 100,000 miles on the car and the cats kept going bad, 3 bad cats last year (all in 2 months of each other), but the dealership fixed them under waranty. Is there a reason for the converters going bad like that? All exhaust work was done after the cats went bad. Thanks

**lancesT/A** · 05-20-2007, 09:42 PM

my car did that after i got new exhaust but after a while it stopped i never understood why it started but someone tried to tell me that it needed to build up pressure or some shit like that, neways i guess i still need an answer... you know i really didnt help

**Redphoenix1998** · 05-20-2007, 09:59 PM

You need a tune. Mixture tables are screwed from the new exhaust because of the different flow rates. Tune will fix it. I should know, I shot fireballs and backfired for a while too

**KiD WiCKeD** · 05-22-2007, 10:20 AM

I got the same problem, the jack ass that owned the car before me put glass packs or some shit on it. They're just steel tubes that looked crimped in 4 or 5 spots. The car will pop alot when its cold outside, but not much if ever when its nice and warm outside. I'm gonna put a Corsa Cat-Back and get a tune very very soon, if that dont fix it i'm gonna be pissed.

**xzaero0** · 05-22-2007, 10:32 AM

Ive only had my exhaust for about 3 weeks now, it happens more at idol than anything about 70-80 degrees. I bought 2 loudmouth2 mufflers off of ebay, I think that I got a good deal. The drivers side pipe hangs a little low, its really no big deal. My total exhaust was pretty cheap only alittle over $500 bucks total but it is a little loud. Im gonna get a tune pretty soon also, as soon as I get my underpully, 160 themo and electric water pump on.

**yellowv** · 05-23-2007, 02:37 PM

Originally Posted by KiD WiCKeD

I got the same problem, the jack ass that owned the car before me put glass packs or some shit on it. They're just steel tubes that looked crimped in 4 or 5 spots. The car will pop alot when its cold outside, but not much if ever when its nice and warm outside. I'm gonna put a Corsa Cat-Back and get a tune very very soon, if that dont fix it i'm gonna be pissed.

Those are chambered mufflers not glasspacks. They are actually very good mufflers and sound great.

**PFM** · 05-24-2007, 12:21 PM

Check and make sure that the sparkplug wires aren't getting burnt into the headers. I had one on the 6th cylinder that was trying to burn a hole in one of thoses MSD 8.5 plug wires. It was causing the car to backfire. if not its tune time.

**LS2Tuner** · 05-24-2007, 01:02 PM

Yes to see the total benefit you surely need a tune.
There is many things that can aid in the backfiring also........Bad(burnt) plug wire,leaking exhaust,rich mixture that causes gas to load up in the exhaust....ect.
Cats will also go bad quaickly from very rich mixtures due to raw fuel in the exhaust..... Someone maybe ported the MAF and screwed the tables all up....

**txoutlaw69** · 06-04-2007, 09:19 AM

why are tunes so fucking much

**LS2Tuner** · 06-04-2007, 10:55 AM

Originally Posted by txoutlaw69

why are tunes so fucking much

How much did they tell you.....?
And how much power did they tell you they could tune into it......?
Depending on where your at makes a difference in what they can charge.
Thats why sometimes it's better to just go with a handheld. Unless you have major mods......Cam,heads,blower,nitrous,ect.

**txoutlaw69** · 06-04-2007, 11:23 AM

$400. i am stock. they didt say how much h/p but dam $400. i need to look into a hand held one

**xzaero0** · 06-05-2007, 10:47 AM

They told me yesterday that a tune would only cost me $250, and that they would put it on the dyno also, to make sure that it was a safe tune for my car.

**TACE02** · 06-09-2007, 04:15 AM

Most speed shops do charge around $400 or so for a tune, but it is a one time price usually. So if you ever need a retune due to more mods all tunes after the original are like $50 or so at that shop. Call and ask.

**xzaero0** · 06-10-2007, 05:24 PM

It was just to help get rid of the backfires, I bought a Predator hand held but I havent used it yet. Gonna see if they can get me a tune for performance and one for Gas Mileage.