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Exhaust backfire while shifting to 2nd.
Topic Started: Jun 2 2014, 03:31 PM (531 Views)
m4ick
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I drove quite a bit on the highway last week and toward the end of it the exhaust drone seemed to be getting louder over time. On my last drive at low RPM under load the exhaust sounded more "gurgly", not pinging but more like a diesel engine. It still drives fine.

Today I drove to work and it still sounds gurgly and the exhaust drone is still louder than usual but when I went to lunch I shifted to second and POP. Stopped at a light and again POP when shifting to second. It did it also on the way back to the office. It happens when you release the gas and press the clutch.

Could this just be an exhaust leak causing it? Maybe letting a bit of O2 into the exhaust? My understanding is that I'm running rich but I'm wondering, maybe I was running rich and now I have a bit of a leak letting O2 in to combust with the bit of gas left in the exhaust.

Any ideas are greatly appreciated. The Geo is allowed to get dirty but it's not allowed to run poorly.
Edited by m4ick, Jun 2 2014, 03:35 PM.
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Scoobs
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:D

Sounds like you broke a weld on your exaust. Less- no back pressure will make it backfire. I love hearing mine do it lol. Make it feel more like a rally car. :)
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m4ick
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LOL. Hell yeah! Thanks for the input Scoobs. I think that's pretty much all it is. I think it was running rich as well, I just bought a timing light and it was at 2* BTDC. :smackface Guess timing it by ear doesn't work suh guud.

I set it to 8 and now it sounds like a ricer with that leak. I think I'm going to do all new exhaust, I've already patched it once and I don't want to be getting under there every few months until my entire pipe is a bandage. I was just beginning to worry about the motor being it's at 166k but I have full confidence it's just an exhaust leak and I was letting it worry me a bit much. After posting I started to think, "You anxious bastard, everyone's going to see your post and think, 'GET UNDER THERE AND LOOK YOU DINGUS!'"
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truckjohn


Beat me to it... I was going to guess Rusted out exhaust....
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mwebb
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FOG

you need fuel and air and heat to make "backfire in exhaust"
an exhaust leak may add the air
but the fuel must already be there

unspoken so far is the simple fact that there should be no fuel in the hot exhaust
and
if combustion was complete then there can be no fuel in the exhaust
so
therefore
it is safe to say

the exhaust leak does not cause the backfire
the fuel does

where did the fuel in your exhaust come from anyway ?

Posted Image
see about 14.225 in horizontal time base
that spike with open exhaust valve is
Backfire
measured with pressure transducer , i know where this fuel came from
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m4ick
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I would imagine the fuel came from the ignition timing set to 2* BTDC. Didn't allow enough time in the cylinder to burn completely before the exhaust valve opened.
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