Injuneer

You are saying that the engine never goes above 1,200 RPM even though "it" (the tach?) shows 4,000 RPM?

I could see where the RPM could be off, due the electronic interference on the Opti signal wire(s), but that doesn't explain how the TP%, the MAP sensor, the MAF sensor, and the injector pulse widths are totally consistent with an engine running at 4,000 RPM.

As far as rhe small range of surge you indicate, that pretty much matches what I said was happening in paragraph #5 in post #12, and I indicated I felt that was normal for yor cam. Your tach is probably reading 100-150 RPM higher than actual RPM, but that is also normal. Tuner might be able to play with the timing vs. RPM to reduce the surge slightly.

If your engine is only surging at low RPM, and not actually running up to 4,000 RPM, not sure what you should look at other than some high voltage wires too close to the sensor wires. But even that is hard to comprehend as to how it could totally cause at least five engine sensors to simultaneously indicate the engine is running at 4,000 RPM. Never saw anything like that in the 20+ years I've been scanning LT1's.

95LT4Z28

i think i goofed. i thought i had stopped the scan before i shut the car off because i rapped it a couple of times before i shut it off. that must be where those numbers are coming from. i apologize for the confusion. but i never moved the car so where those mph numbers are coming from is a ???. so other than cleaning up the IAC - everything else seems within specs? or do you have any suggestions? thanks for your time ---al

Injuneer

I explained the possible reason for the MPH readings in the next-to-last paragraph of post #12.