We've been having the same problem with my wife's 98 for the last year and a half. Sometimes it will not start - but sometimes it will start, only to fail a couple of miles down the road.
I am pretty sure it is electrical, because when it happens, all the guages go dead, including the tach while the engine is still turning. It is driving us nuts. I'll paste what I posted on the general technical forum yesterday. So far, no one has come up with a solution, but my guess is that this has happened to others.
It may require replacement of the entire computer, since most of the other likely culprits have been replaced.
I can say that I have an old Ford Ranger pickup that demonstrated similar symptoms. I finally gave up and took it to a mechanic. After 3 days of fiddling and parts replacing, he found that the main harness to the computer had loosened at the firewall where underhood wiring connects to the in-cabin harness.
Again, here's what I wrote on the general tech forum:
My wife's baby, our low-miles (80k), 5-speed, 98 T-Top V6 coupe with the "performance and handling package" is driving us crazy.
About a year and a half ago, the car began having hard start moments (sometimes it was fine), and began cutting out on the road. Tach went to zero even though engine was still turning. No guages. No check engine. No codes.
We took it to our local mechanic and after replacing the crank sensor, it ran fine for two days and then began dying again. He replaced the coil packs and then the car ran fine, started easily and did not give us any problems for a year and a half.
Two weeks ago, right after passing its annual emissions test with flying colors, it started having the same exact problems. Would run fine, then on the next attempt to start -- would not start. Wait a day and it might start, after running roughly and belching smoke (suspect it had loaded up with fuel because I could smell gasoline every time I tried to start it), it would clear up, run fine, but within minutes of driving it down the road, it would start bucking, tach would drop to zero and it would die.
So...after doing a little research, I first replaced the cam sensor. No change. Took it back to the mechanic who'd worked on it year before last. He replaced the crank sensor again. No change. Replace the ICM under the coils. No change, but it did start once. AND he WAS now getting a code for a bad cam sensor.
Replaced the cam sensor I'd just installed and voila -- started and ran. He kept the car for two more days, letting it idle and runing it on errands whenenver he could. No problems. Saturday, I went to pick it up and pulling the long hill about a mile from his shop, it died, suddenly without any bucking.
I read somewhere on the Net that someone had similar problems and it turned out to be a wire, that was broken inside its intact insulation that lead to the crank sensor.
The mechanic is now trying to restart and will wiggle all the wires and connections he can find. We've already spent about 500 bucks on this thing and could easily spend another 500 before we debug it.
Has anyone seen this problem? Wanna by a low miles Camaro, LOL?