OK, I have had a problem now for many years and am very frustrated about it.
I have a 94 Z28 6-speed with a relatively stock LT1 (including good ol'
Opti-Spark). Here's the problem: at light throttle (between 1500 and
2000rpm, all gears), the engine runs rough and almost seems to have a miss.
I can feel the car kind of "surging" and it is really annoying. If the
normal feel of a smooth running engine were described as simply
"mmmmmmmmmmm", my engine would feel like this:
"mmm-da-mmm-da-mmm-da-mmm-da-da-mmm". To hide the problem, I end up hitting
the gas a little harder, but then it slowly -- and obviously -- accelerates
beyond the speed I would like to be at and then have to slow down. I
constantly repeat this pattern. My alternative is to pick a lower gear and
just get the rpm's up a little higher. In trying to fix the problem, I just
had opti-spank replaced (3rd time). Could a vacuum leak be causing the
roughness at certain rpm's? Can the fuel pump do this (and how)? The only
upgrades I have are a borla cat-back and K&N air filter, and I only have 65K
miles on the car.