To start I have a 96 LT1 heads and cam car(very tight lobe sep), stock bottom end. I continue to get random misfires above 2500rpm. I have Autotapped it and found the misfires are all over every cylinder except at idle. I can hear intermittent popping in the exhaust if i hold it at 3k. Car seems to be down on power.

What I have done so far besides scanning w/ autotap. Check fuel pressure. Pressure is good. Plugs and wires replaced. autolite 104`s gapped at .044 running 11.1 to 1 compression. I have an MSD 6a box and coil have unplugged the box, it made no difference. Checked all grounds and cleaned them. Replaced o2 sensors w/ new GM ones.

I currently have removed the old opti and have taken it apart. Found carbon whitish buildup on 8 terminals in cap and rotor end is black. Would this be considered a bad opti? Or is it just enough buildup to cause the intermittent misfires across the board? I`m wondering if I am having a problem now since perhaps I`m running too much gap at the plug w/ my compresion ratio and an msd ignition. I`m hoping to see if anyone else has run into this issue, and was it opti related or not.

Please help very frustrated....

 

It would appear that you have adequate spark and the corrosion you saw was completely normal for a distributor.

Why don't you consider putting it on a dyno to see what your AF ratio is at the point the problem appears. It may be that you need a little more fuel. It also might not hurt to get the compression on at least a few cylinders to see what effect the overlap of the cam has.

 

Mine had an identical problem on a stock motor.... it was the OPTI...
Just my 2 cents...

 

It has been on a dyno, a/f was fine it was tuned the same day as it was on the dyno. Of course it was tuned for WOT. I t would be interesting to see if the a/f is out on part throttle , but on autotap the a/f is diastolic 14.7 to 1. I know its not accurate at WOT, but it should be for part throttle.

Have not done a compression test.

Thanks to both of you for the replies. Any other suggestions other than the compression test?

 

You said you checked fuel pressure... was that ay 5800-6000 rpm on the dyno? Fuel pressure can fall off up top and be fine at idle, still means you need a new pump. (Or filter, or injectors,or...)

 

fuel pressure was checked by running the guage w/ a long hose and taped to the windshield for some real world driving conditions including WOT! Lol.. No drop in pressure.

See why I`m so stumped...

 

Check the side of the coil for telltale white marks or tiny cracks indicating that it is firing through the case and usually toward the metal laminations. Look for sparking around it and any wires in the dark,

 

Thanks again for the help, ckecing fo sparking around wires in the dark was my very first try to diagnose it.

I`ll check around the coil though. Thanks.