ok, so here is my situation. I have a 30th anniversary special edition z28. it is a v8, it has 78,000 miles, put a new clutch in her maybe 3,000 miles back, just changed out that damn opti-spark shennanigans as well as water pump. It ran great right after changing all of that out. Then i screwed up and let it sit for a weekend while i went out of town with it on less than a quarter tank and then it didn't want to start. I went and got some more fuel put it in then eventually got her to start. It ran good for about a week and then i noticed the tach was all over the place while on the expresway the motor sounded fine. Then I made it home cut it off and the next morning on the way to work it didn't want to start. I am hoping it is just the fuel filter having build up in it, I am planning on changing it out today. I was just hoping some some of you guys could give me some pointer or other things to look into or tell me what i can do about the tach. Thanks guys

 

check the opti wires and make sure there is not a lose plug in. check the wires to the ignition modual and coil. bad ignition modual can do what is happening to u. have u changed the spark plugs? new fuel filter is a good start.

 

Does your tach look like it is surching around and stubling and stuff. This sounds like opti failure. It picks its times not to start than wait 30 mins and it will start and act fine. Is there an oil drip from your engine after the new opti install?