97 Trans Am LT4 Bad Backfire, minor misfire

[FTA9597]

Hey everyone,

I have a 1997 LT4 Frehawk in my 95 TA. I have this horribly, HORRIBLY loud backfire at idle. I have a custom Monza exaust system, true duals, no crossover, this makes it east to tell the source of the backfre. Its only on one side of the engine. Temp runs normal, but its only when the thing is running open loop. Closed loop there are no problems at all. I think it's the Opti-spark system. I'm debating a distrubutor problem (which could make sense, considering how the opti divides the leads for each side of the engine) or a minor valve train problem. Also, it seems that the odd side isnt pushing as much air as the good running side. I check everything stupid so far, such as sensors, wiring, vacuum lines, pretty much everything exept fo the valve train and the distibutor, due to my lack of my own tools.
I'm getting pissed off about this one too. Sometimes it will cease with gold eagle octane booster, but only gold eagle.
Performance wise, above 1150 RPM's everything is fine, idles at + - 850 RPM's

Any other details just ask.

thanks

Al

PS the backfire is really only annoying, but i have no cats and no mufflers on there with 3 1/2 inch pipes so I'm sure its not hard to imagine the sound. We compaired it with a magnum (.38 special) and they are about the same.

[FTA9597]

I just check the valve train and everything seems to be in very good order, plus the misfire wap is coming from both pipes now at a completely random frequency...

Input?

[ikeyballz]

errr.. couldnt the misfire allow some (unburnt) gas to leak past the cylinders into your big exhaust, and since your FI, wouldnt the heat from everything cause the backfire? as in..if you fix your misfire wouldnt the backfire go away too?

@ higher rpms, wouldnt the misfire go away, since the exhaust gases are exiting faster? O_o


so..misfire fix first? new opti? idk..

[FTA9597]

yea the mis usually goes after about 1000 RPM closed loop and 1200-1300 open loop. I'm prety certain its the opti.
I'm converting to ignition packs i think just because it's easier and way more reliable.

Fix Your Opti-Spark in an Hour or Two
http://www.delteq.com/index.htm

[FTA9597]

Fixed the problem, and boy am I pissed.

When I swapped out the old plugs for new ones I had a misfire before that.
The old plugs had a few issues just because they were old as sin.
The new plugs were NGK g powers. I never used platinum plugs like that before, so I did not change the gap, as the packaging states not to(i thought this was stupid).
Advance Auto gave me the wrong gap size off of their computer system (AllData?).
I was running with a .055 gap instead of a .o35 gap like iwas supposed to have. fixed that and checked everything else. No more mis or fire haha.

So i guess we should all check the dumbass problems first then.