Backfire Issue

[5.0H]

Alright guys so I've got dual exhaust (straight pipes from catback), GT mufflers, frpp CAI, and bama tune w/ the sf3 tuner. I have an issue with the engine backfiring pretty badly when I drive it the first few minutes after starting it up. It's really obnoxious and makes the car sound like absolute shittt. I had noticed the same issue before all the mods but it wasn't as bad/noticeable. Am I maybe running rich with the tunes or am I just worrying over nothing and just need to let the car and exhaust warm up more before driving? Figured I'd ask for suggestions before going to bama for diagnostics and what not.


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[TexasBlownV8]

Should be no backfiring even when cold. Are the spark plug wires on the proper plugs?

 

[5.0H]

ummmmm they should be. I'll check when I get home from work and follow up here.

 

[5.0H]

alright so I went under the hood and checked things out....here's the way the spark plug wires are hooked up currently:

3-----------6
2--ENGINE--5
1-----------4

and the coils are set up the same way the stock coils are labeled (I have a screamin' demons)

1 2 3
5 6 4

There are no markings on the screamin' demon so is it possible that I should be running the bottom row 4 5 6? someone with a screamin' demon chime in...

edit: just looked up the installation guide on AM for the screamin' demon and it says to maintain the 123,564 setup...not sure where to go from here. http://1.cdn.lib.americanmuscle.com/files/50200.pdf

 

[5.0H]

 

[5.0H]

Well I had a coolant leak and I just took it over to a buddy to pressure test it...looks like an intake gasket leak. So maybe that'll have something to do with it. Who knows at this point. I'll keep you guys updated.


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[amustangrocks]

the 4.0`s make alot of popping noise if you rev it up then back off the gas, with no backpressure from the duals if they are not under load. the race tune might add to that, but not a all out backfire. i know a guy with a stick that jumped his timing and dropped a valve from a redline rev addiction.

pretty rare to see a intake leak, but that cant be good. interested in the outcome.

 

[5.0H]

This is what I'm dealing with. I got home from dropping it off and this is what was in the garage from a day of sitting there. Coolant on the cardboard and oil on the concrete.

Yeah I was so surprised when he tested it and we saw it coming from the intake. We thought it was just the water pump. Now he's gonna be changing the pump and the intake gasket. He's gonna replace the valves and get a nice machined surface on the intake to make a good seal. He does good work so I'm not worried. He said its possible that it could be a head gasket but I'm crossing my fingers that he doesn't have to go that deep into the engine (and my wallet).


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[TexasBlownV8]

There's no water that passes though the intake manifold!!!

However, on the '05, you do have a 'heated throttle body', where coolant runs through the throttle body. If water is getting in FROM the intake, you're probably getting water in from there.

A short-term solution is to bypass the heater hoses on the TB (there's various 'heated throttle body bypass' writeups around). You do not need coolant running through the TB; the '06 and up did away with it.

You could have a 'head gasket' issue as well, but not as likely if water is in the intake.

Most water leakage comes from the thermostat housing; the water pumps are pretty good and not the cause of many leaks.
The oil, well, that could be coming from the intake as well, but might be from elsewhere.

If you need a replacement TB or intake manifold, I have them from a '06, which will fit just fine.

 

[5.0H]

yup you're correct. wasn't really thinking Dave had mentioned that he thought another possibility may be the thermostat housing. I will let him know that I have a replacement TB and/or intake manifold on hold if I need them. Thanks once again mike

 

[5.0H]

good call Mike...turned out to be the thermostat housing gasket! Relatively pain free fix and didn't hurt the wallet like I thought it would as for the loud popping/snapping, well it's still there and it's still obnoxious

 

[TexasBlownV8]

No cats will do that popping noise

Glad you found the water leak...where's the oil drops coming from?

 

[amustangrocks]

t stat housing is really common. you still have a oil leak, might just be your drain plug or your filter.

 

[5.0H]

I kept the factory cats. Straight pipes went in starting right after them.

Dave says the oil is coming from the drivers side of the engine right around the top of the block. I haven't had a chance to look myself but whenever I pull away from a spot there are two or three drops on the ground. I had my oil changed last week and the guy put regular in instead of synthetic. I was in a rush and didn't notice the price difference until later that afternoon (did it at lunch). I drove 100 miles that afternoon for work and when I realized what had happened, I took it back to them to drain the oil and put synthetic in. Talking it over with Dave, he said how switching from synthetic to regular can do bad things to your gaskets but he didn't think 100 miles and a few hours was enough to cause any problems. Who knows though...maybe the regular oil just being in there was enough to screw something up. Either way he's gonna take a look at it after the 4th when he has some time. Until then I'll just be pissing away a few drops of oil everywhere I park


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[TexasBlownV8]

The new engines are not as bad in switching between the two, as the gaskets are more tolerant.
You could be getting some oil leakage around the breather tube at the back of the valve cover. You should check the oil filter, as it's probably not on all the way tight. I dont trust those oil change shops.

 

[5.0H]

Alright I'll definitely check that out tomorrow. and I know I hate going to them too...expensive as hell and they almost always do a shitty job. My engine bay is immaculate and he dripped oil, coolant, and windshield washer fluid EVERYWHERE. This is the last straw for me. I'll be changing my own oil from now on.

 

[TexasBlownV8]

The good thing about changing your own oil, you know what you're putting in, and you also look underneath and can spot other issues early. And you do it right.

 

[RunnerInTheNight]

I just about blew my thermostat housing to bits, thankfully I noticed the smoke and pulled over. Good luck with the popping.. I had it I was told its just the backpressue making its way out... I don't think thats the proper wording but I think ya get what im saying.

 

[5.0H]

I just about blew my thermostat housing to bits, thankfully I noticed the smoke and pulled over. Good luck with the popping.. I had it I was told its just the backpressue making its way out... I don't think thats the proper wording but I think ya get what im saying.

thanks man. I'm coming to terms with the fact that I just need to let my engine run for 30 seconds or so before I pull out of the parking spot whenever I start the car. It seems like the computer just needs the time to make adjustments to get everything straightened out before I start driving. It doesn't matter if the engine is hot or cold. I tested it out a few times and turned the car off and back on while doing about 40 with it in neutral. After turning it back on, I continue crusing in 4th gear and as soon as I let off the gas it pops. But give it 30 seconds and it's good to go. Whatever...it is what it is.

 

[dark steed]

Is this popping noise you're referring to coming from the exhaust? My understanding of a true backfire is when combustion occurs before the intake valves are closed and the flame exits through the intake manifold/carburetor/throttle body
Another definition is Is unburned fuel igniting in the exhaust system, which sounds like what you have occurring.
I have factory cats and straight pipes w/no mufflers on my '07 GT/CS and this is a common cold start occurrence for me. If I run it up to around 2000 rpm and suddenly let out of it I will get a pretty loud pop, or if idling down a hill in second gear it will do a series of lesser pops when cold...I actually kinda like the down hill thing!


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