cobra backfire ?????

actually, my car does the same thing. I think it is a fairly common occurance, and shouldn't be anything to worry about. do a search on svtperformance.com

My 03 Mach does the same thing, but only on quick shifts & usually between 1st & 2nd. Im not sure what causes it because my motor only has 39k & is basically stock besides a C&L 85mm, MRT Catted H pipe, & Bassani catback. I cant remember if it did it when the car was stock. I think its a 4v thing.

Yeah... i'm pretty sure that just goes w/ the four valves... mines does it... I kinda like it.

I don't think you answered the check engine light question unless I overlooked it. Take it to AutoZone if there is one in you area. They will do a check engine diagnostic (FOR FREE) and can tell you what the problem may be. Just tell them the check engine light is on whether or not it is, and see what pops up. I blew a vacuum line off my car (and got the check engine reset, which came back on the next day)and took it there and they said it most likely was the vacuum line. However, the free diagnostic did raise a few eyebrows of possible reasons such as O2 sensors and catalytic convertors. May be worth checking out.

rrohrig said:

I don't think you answered the check engine light question unless I overlooked it. Take it to AutoZone if there is one in you area. They will do a check engine diagnostic (FOR FREE) and can tell you what the problem may be. Just tell them the check engine light is on whether or not it is, and see what pops up. I blew a vacuum line off my car (and got the check engine reset, which came back on the next day)and took it there and they said it most likely was the vacuum line. However, the free diagnostic did raise a few eyebrows of possible reasons such as O2 sensors and catalytic convertors. May be worth checking out.

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Yeah, autozone FTW! I took my daily driver Honda car by a NAPA auto & truck care center cuz it was closer than autozone, and I buy alot from the NAPA parts next door, so I go in and ask to get the codes ran for free. The guy at the desk is like "alright then lemme get u a service guy" so he comes out, is like "yeah just fillout this form" and I'm like "well I just want the codes checked, it has a CEL, ok?" and he responds with "no problem no problem, we just need some info for our records." Before I even start I ask again just to make sure "so theres no cost to get the codes checked right?" and this joker is like "It's an introductory fee of $83.65, but then if we find any codes we'll tell you what each one means, and what might be wrong!" ...acting like that was a big accomplishment! So long story short, drove a bit farther to AutoZone, got the code worked out, drained/filled transmission, good as new

I would figure your backfire is coming from an extreme rich condition, and/or an ignition problem (have your coilpacks tested, and replace the wires if they are old).

rrohrig said:

I don't think you answered the check engine light question unless I overlooked it. Take it to AutoZone if there is one in you area. They will do a check engine diagnostic (FOR FREE) and can tell you what the problem may be. .

Click to expand...

Not really. All they will do is pull the code and tell you what parts to buy. That is what we call a parts changer, not diagnosing the vehicle. They won't fully test and diagnose the system, just give you some guesses. Also if there are no codes stored or in there, they can't do anything. Sometimes you can get parts that fail, but not necessarily set a CEL.

My 03 would then the valve blew.valvetrain tic sounds like exhaust leak . Try doing a compression and leakdown test

Back-fire could be a few things, most ignition related than anything, plug wires, coil, do you have any codes (engine light) on. Many people need to get away from these canned tunes, example I had a customer come in with a 96 he had a blower installed on, he wanted us to tune it. After data logging the car, it was out of fuel, out of spark and the maf pegged yet it ran okay, there is a example of a car if the customer would have made a pass on his mail tune, boom he would have needed a shovel to clean up the mess, however in your case it sounds like a mechanical issue not tune related but more ignition related.