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Discussion Starter #1 (Edited)
I have an LT1 in a caprice wagon. New optispark, new wires, engine is not throwing ANY codes at all. However, I feel a distinct miss throughout all RPMs. At idle, under load - it doesn't matter. Car starts right up - within 1/2-1 rev of the starter. Idles with just a touch of a miss - every revolution without fail. Engine appears to idle well if you're looking at it, but if you put your hand on it, you can feel it.

I JUST bought the car so I am a little pissed.

Vac reads 18.5 at the manifold. All the plug leads are carrying spark. There were a few vac leaks at the mani that I took care of. Replaced the PCV. Tightened the manifold down - some of the nuts were borderline hand-tight. No ticking or knocking to speak of.

Initially, I thought it was a resonance/harmonics issue with the dual flowmasters not having any sort of h-pipe, coupled with the fact that the dolt who installed them didn't use isolation mounts on the rearmost section. However, at a very low cruise RPM, just strolling along at about 35 and in a high gear, you can feel it "chug, chug, chugging" along.

The miss is dead-on rhythmic. At this point, I am thinking it may be a fueling (injector) issue or bad plugs.

Thoughts? In the past, if I've borked up the firing order, a typical SBC will barf out of the intake or pop though the exhaust, so I don't think that is the problem. I'll be checking anyway when I re-do the plugs.

O' LT1 gurus of the forum, I seek your guidance...
 

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It sounds like your miss is load related, so I would start with your coil and icm. Have you done the icm cooling mod? Some auto part stores can test your coil and icm. Have you used dielectric grease both ends of the coil spark plug wire? I would start here, then check for codes, then datalog. One other place to check is the wiring harness that goes from the opti to the wiring harness on the passenger side of the intake manifold. Make sure the wires are not frayed, or the connector has corrosion on it.

hth

andy schuck
 
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