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Discussion Starter · #1 ·
Today i noticed while idling that my driver side exhaust was making a popping noise/ backfire noise? every so often. When im driving i dont hear it at all only at idle. Any idea what this could be? I recently filled my tank with premium 93 gasoline, prior to this i never heard the popping at idle. Would this have anything to do with the noise?
 

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Run through the tank and put 87 octane back in, UNLESS you have a PCM tune that require the higher octane gasoline. 93 octane gasoline has less energy in it but also resists burning hence why it it generally required for higher compression and power engines so it doesn't experience detonation. However the 94-96 B-body LT1 engine in stock form with stock tune only needs 87 octane. - Peter
 

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couple other things come to mind.

cracked exhaust manifolds and/or broken studs.
exhaust valves burnt or adjusted too tight.
 

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Discussion Starter · #6 ·
the exhaust manifold are those greyish things coming off both sides of engine correct? i just visually inspect those with my eyes for cracks? how would i check the other thing you suggested? i wont be out of gas for at least till mybe tuesday or wednsday to go back to 87 gasoline.
 

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FWIW I never have had popping when running a higher octane gas, I am sure that peter is correct, just hard to believe in my eyes.

w$cb- yes they are the grayish things coming off the side of the engine, really I am not entirely certain that you have a real problem with anything on the car, does it run ok otherwise? Does the backfire sound like shotgun? Doubt it but had to ask. when it is doing it if you rev it does it go away and then come back a short time after. I still think that it is a condisation issue in your exhaust causing the noise. My 95RMS does it if I let it idle for a bit, I am running a 93 octane tune with 93 octane gas, so I don't know. Basically what I am saying if it runs fine otherwise, don't try and fix what ain't broke :)
 

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Discussion Starter · #8 ·
You described it almost to a T. Not shotgun, more quiet but still very notticeable popping when idle. When driving I've rarely heard it. I can't see ur other questions while posting but u describing it what it is.
 

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For the exhaust manifolds you can feel around the back of the drivers side exhaust manifold (while the engine is cold of course :) ) to see if its missing one or both of the rear two exhaust manifold bolts, though I haven't seen the drivers side manifold crack myself. You may be able to visually check if the bolts are there but its harder to do especially with the manifolds going over the spark plugs makes things a little harder to visually check. As far as the passenger side manifold goes, you can get under the car and look at the space between the rear two exhaust ports on the manifold as that is a common place for it to crack. Also the rear most bolt may be broken on the passenger side as well.

The reason I suggested switching back to 87 octane gas is because if the popping noises only started after switching the gas to 93 octane then switch back to see if the problem goes away. Of course popping noises can be caused by other means, but at least that is a place to start and easy to do. Also by running the expensive gas in the car generally means having to pay more money which adds up over time(especially with gas prices inching their way back up again just had about a 15 cent/gallon jump around me), and if the engine can't benefit from the higher octane gas then why spend the extra money. Of course, as stated in my initial reply, if you have a PCM tuning that had advanced timing and whatnot and therefor requires the higher octane gas, then by all means run it so you don't run into knocking issues. - Peter
 

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Discussion Starter · #10 ·
Sounds like I'm freaking poppin popcorn under my damn car! Someone in florida heeeelp!
 

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Discussion Starter · #11 ·
Ok so I took it by a local muffler shop and they said my engine is "jumpin" and that I have a misfire, causing the backfire popping noise. Moving this thread to engine problems I guess thanks all.
 

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You engine is jumping huh, interesting, I truly doubt it is a misfire. It would run like hell if that was happening, you never confirmed this for me? I really don't think that you are having all the troubles that are associated with a misfire, could be a bad tank of gas. Run the gas out of it and fill it up with fresh and see what happens. I could be wrong, but you are asking for a lot a time and troubleshooting on your end if it is a bad tank of gas honestly. Peter said it all in the beginning, let the gas run out of the car and fill up with new probably 87 octane since you started having this issue after a tank of new 93 gas. Just saying man and not trying to be a dick, but you maybe troubleshooting a problem that isn't a problem at all.
 

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Discussion Starter · #13 ·
I ran it fully out till I died on side of road then I walked wit the gascan and put 87 back in. Still have the popping noise under the car. I took it this morning to an exhaust shop and they put it on a lift and before lifting he said look at the hood see how its "jumping" and every here and then it like jumped alittle. He said before opening hood it has a misfire causing the jump. They opened engine and never lifted high enough to see my exhaust he said spark plugs, wires, coil, and or opti but he wnwants 60bucks to scan it and see for sure what it is. I had a doc apptmnt in like 20min so I passed as well as it sounded high. Have a possible buyer for my car and would like to pass it on in good shape.
 

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That is just weird man. Honestly if it isn't popping any codes, and as long as the check engine light works, them scanning it for 60 bucks isn't going to tell them anything. Maybe if one bank is running lean or rich, I don't know maybe they have a magic scanner :) Wonder if a semi clogged cat would cause this issue?!
 

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Discussion Starter · #15 ·
Well I told him I heard auto parts store scan for free why don't they and his reply was that they use a cheap scanner tool unlike what they have at an mechanic shop such as his. Also I remember it rained for two days straight and my car is lowered so I splashed thru a few puddles that made my steering wheel lock up a few times, not sure if that helps.
 

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You got the Opti wet in all probability and it may have a crack/broken seal and got moisture inside. Is your vent harness working?
When did you last change wires? Is there arcing when you check it at night?
 

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Discussion Starter · #17 ·
Ill have t get back t u on everything, all I know was plugs and wires were changed about 2-3 months ago.
 

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It's crazy that I get alot of info but can never actually help at all...but yes I also believe it is a problem with your exhaust manifold....but only because I just had my drivers side manifold replaced to eliminate the same noise your talking about...strong rumble of the engine like it should sound but every few seconds it's sounds like someone is hitting the bottom of an empty 5 gallon paint bucket....trust me I know the sound....drove me bats! I'm in Jacksonville fl and am also running high octane without a tune of the cars computer...but I luckily ran into a man with a dynotune machine at Autozone! Getting a tune tomorrow from him for $75....what all should I ask him to tune besides the changing of the gas type?
 

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There are alot of things that can be 'adjusted' with a tune, you just have to know what you want. I don't know why you guy's insist on running 93 octane, unless you are looking for that last .01 of a second in the 1/4 mile, other wise you must just have $$$ to burn. Tuners's THAT KNOW THESE CARS, can do alot of little thing's that will make them run better without you doing anything to them.

Try the search button and do some research.
 
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