So I have a 1994 non zr1 it has no performance parts and is all stock. My problem is that I have had a rough low idle for a year or so now, runs about 500 or so rpms at idle in gear, you can see the dash lights dim back and forth with the idle and can feel the car shake a little like a lifted cam. I have replaced plugs, wires, distributor, map sensor, egr valve. I had it at the dealer for three days, they did an induction cleaning on it, and a compression test, and then gave up. Now the big problem. I don't drive the car to much long distance, but in September I had to drive about a 6 or so hour trip, that's one way. Car did great going down, but when I was leaving the hotel to go home the car shut off in the parking lot, just like I turned the key, no stumble, or sputter. But it started right back up, and I headed down the highway. About 5 miles from the hotel, while doing about 75 mph on the highway it shut off again, same way, no warning, I left it in gear (drive, it's an automatic) and I shot across three lanes to get to the shoulder, before I get there the car springs back to life on its own and takes off down the road like nothing happened. Everyone I tell this to has never heard of a car doing that. It did this two more times, with about 5 to 10 miles between. So I stopped and filled up the tank which was about half a tank, thinking I got some bad gas. After that no more problems the rest of the trip which was still at least 4 hours. About a month or so later this has returned, it randomly shuts off like you turned the key, if the car is moving it will restart on its own, but sometimes it will do it like sitting in bumper to bumper traffic, or when you go to pull out of a parking spot. When it shuts off, the rpm gauge goes to zero, but everything else is normal just like if you get in and turn the key, other gauges still read normal, but the battery light comes on, weirdly enough the engine light does not, the radio stays on, and lights stay on. And it Has never given a code. I really need some help, cause I drive this car pretty much everyday. Thanks guys!

 

I have a similar problem with my stock 1993 anniversary C4 engine. but mine restarts after sitting for 5-15 mins. and will restart everytime I turn the ignition but not stay running unless I wait before trying to start it. also no trouble lights are on and it runs fine for 5-10 miles then shuts off again.

 

You could be overlooking something small like a vacuum leak, I've seen this cause some weird things, so, it's worth checking all your lines. Listen for a hiss, spray in some brake cleaner on the lines and listen for a change. Your car is getting some age on it, they'll start to crack.

Also, check the maf. If the engine thinks you are getting WOT, I've had older vehicles flood and kill the engine. Another time, it was a pin hole between the map sensor and manifold. Hard to find, but the computer won't read the pressure thinking its getting more air than it is.

Easy way to tell if it's flooding is to look at your plugs and see if they are black.