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Slight Backfire

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Old 04-16-2012, 07:10 PM
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Car: 91' Z28. 70' Dune Buggy
Engine: LSX Cam/Full Bolt ons
Transmission: T56
Axle/Gears: 4.10
Slight Backfire

I have a 91 305 TPI Auto
When in neautral, wether warm or cold, if I rev the engine I get a slight backfire under deceleration. Its just two quiet, but noticeable pops.

When driving if I down shift to 2 or 1 I can hear it back fire aswell. It's nothing loud, but just wondering if its a problem, and maybe can be part of the reason to my suckish fuel mileage.

The car drives fine though.

Is this normal, or am I running rich?
Old 04-16-2012, 07:51 PM
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Car: 1985 Iroc-Z
Engine: 1 BA 305 TPI
Transmission: Probuilt 700R4 - 2800 Stall Midwest
Axle/Gears: 3.42
Re: Slight Backfire

When was the last time you changed the plugs and wires?
Old 04-16-2012, 07:54 PM
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Car: 1986 Camaro Z28 IROC-Z
Engine: 350 Tuned Port Injection, for now.
Transmission: 700R4
Axle/Gears: Posi - 3.23
Re: Slight Backfire

I have that too. But mine only does the pop when i use the engine to deaccelerate (shift from 4th to 3rd). I would say its normal. My bro in laws does the same thing. My plugs are 2 years old and have about 4,000 miles on them.
Old 04-16-2012, 07:55 PM
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Car: 1985 Iroc-Z
Engine: 1 BA 305 TPI
Transmission: Probuilt 700R4 - 2800 Stall Midwest
Axle/Gears: 3.42
Re: Slight Backfire

Another thing to check is your timing.
Old 04-16-2012, 08:35 PM
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Car: 91' Z28. 70' Dune Buggy
Engine: LSX Cam/Full Bolt ons
Transmission: T56
Axle/Gears: 4.10
Re: Slight Backfire

I just bought the car last month. I'll replace the plugs and wires this weekend and ill see if that helps. If not ill check the timing.

This question isn't threadworthy, but my 305 will almost scare me when I'm driving alone, but with a 200lb passenger it is alot slower. I go from about a 6-7 sec 0-60 to about a 9-10sec. With my v6 cherokee I couldn't tell when additional weight was in the car.

Does everyone's stock 305 do that, or maybe I'm missing out on a little power.
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