1998 Silverado backfire

Hello, new to the forums and from what I've seen you guys are an awesome help to everyone posting here! Anyways, I bought a 98 silverado about 6~ months ago...114,000 miles, 5.7 vortec, automatic and it came with a single, original exhaust and I guess I didn't notice any problems because I never got on it but....about a month later I got dual exhaust put on it, no mufflers, left the cats and now I notice some issues...


First, the day I got home I took out on an old highway, put the pedal down almost half-way..and I hit about 30 and it died, had to throw it in neutral and start it, so I was like woah, weird...so I got to my turn around and tried again...but it didn't do it again.

I don't remember if it did it before it died that one and only time but now when it shifts' into the next higher gear picking up speed it makes a pop like a backfire, not like obscenely loud but it is definitely heard in the cab and by anyone outside.

Now, to the question...I am not sure when it had a tune-up last or anything. But I am just wondering if that could be a tune-up problem or could it be the exhaust system? There is no check engine light so I didn't figure it was the o2 censor but I could be wrong.

The people that put the exhaust on are very bad though. I have 2 leaks in the exhaust, that I took back to have them fix like 2 days later, they said it was fixed and then a few days later I found the leaks again...had another guy tac them up and still they have leaks. . I am not a welder and I don't own one to fix it myself, but could this be the problem? I didn't think it would pop to some pretty small leaks in the welds but I am no mechanic.

It has never died again, but it is weird shifting as it pops and feels like it loses some power sometimes unless you really put the pedal down but what types of issues could these be? Any help is appreciated, Thanks! a leak anywhere in the exhaust system can cause a backfire thru the tail pipe. theres allways a little unburned fuel in the exhaust stream, and the exhaust parts are hot. if a little air gets in, itll ignite the fuel, kinda like what happens in the cylinders, and youll get a pop out of the tailpipe.

as far as when it shifts, as soon as it upshifts into the higher gear, the rpm's drop and for a fraction of a second the exhaust is a little richer then normal. that small amount of extra fuel can increase the chance of a backfire if theres a leak.

u should get it to a competent shop that does exhaust work to get it sealed up. or even a machine shop with certified welders thats willing to tackle it. if nothing else, this could be a safety issue. if air can get in the exhaust system, fumes can get out, and if they get drawn into the cab, your lungs wont be happy.

if fixing the leaks u know about dont solve it, the whole exhaust system should be checked, from the manifold back, to make sure its sealed up. from the sound of the job u got, there could be leaks u aint found yet. Awesome, quick reply! Thank you!

Well I just got off the phone from another exhaust shop. He told me the only way it could really make it backfire, or pop is if the leak is really big. I am definitely not saying he is right over you, but that is just what he said. Now, I do know the exhaust shops around this small town Iowa area, have turned out to be pretty bad. But, he also told me that I might need mufflers due to backpressure, while on somethings I would believe that but I have heard the same trucks on youtube, and in my area with no mufflers, with cats still intact sounding nice without the backfire.

I noticed there are no y's in my pipe, could that be any factor because another guy told me that true dual is nice but you have to a balance pipe due to one pipe being longer than the other. Just asking opinions on what you, or other people think while I get someone to get this sealed up.

I checked the rest of the piping and other than the leaks I know of I haven't felt air, or seen the condensation coming out on the ground. And I get a LOT of condensation so I would definitely notice.

Thanks again, sir. well, theres a lot of things that can cause a backfire. i just zoomed in on a exhaust leak since u said u knew of some. i aint got much experience modding a exhaust system, so its hard to say whats going on without actualy seeing it. again, if they had the manifold off, it could be that it cracked when they put it back on, or maybe the bolts wasnt torqued right and there could be a leak around the gasket. u would realy need to have the system inspected by someone competant in exhaust systems.

i wouldnt suspect a backpressure problem. if anything, removing the muffler would reduce backpressure, not increase it.

Maalakai wrote:Thanks again, sir.
Well, I was doing some research last night and came across a pipe chart...unless i'm really dumb and misread it the stock pipe for my single exhaust would be 3Car Repair Talk's forum.