We have owned four C4 models
Here is a short novel about them:
1985 Coupe w/ auto trans
1986 Pace Car convertible w/ Auto trans
1989 Coupe six speed
1990 Coupe six speed
For the most part, the 85 was a fantastic car considering how much abuse I put it through. In other words, I was 18 years old with a nearly new Vette in my single college years. I went through four engines. Never blew one, just always in the pursuit of more power. I was going for a hotter engine in late 89 when the aftermarket had yet to catch up with them. I had to follow in the footsteps of Lingenfelter etc. That car went through tons of tires, three or four paint jobs. two water pumps, four transmissions, two sets of shocks, two sets of interiors, two windshields (that was my fault-don't close your hood with large tools sitting on the cowl), one set of injectors, one fuel pump, etc. etc. This is not typical as this car got raced, and went for months when I don't think I shut the engine off except to change the oil.
The 86 was soooooooo sweet when I bought it with less than 50K miles. I had to put a rear main seal, valve stem seals, belt, hoses, brake pads, and really strange, a left front lower ball joint. The problems it had were a direct result of not being driven. The soft seals on the car just dried up. I sold it just over 50k miles and in fact it now belongs to a member here at CACC. It has passed through two owners since I last saw it, and happend to see it a couple of months ago sitting at a local sports bar and left a note on the windshield.
The 89 was Nikki's first Vette. I bought it from a wholesale yard in "as is condition". It took me about four weeks to get it safe to drive as it was missing the brake resevoirs, Mass Air Flow, etc. etc. The prior owner had yanked the check engine light to mask the calamity of problems lurking under the hood. This car had been abused. We bought it with about 68K or so on the clicker. It had obvious collision damage that was poorly repaired, and the electrical was all goofed up from a previous Bubba mechanic. Okay, after getting it together it was a good freaken car. I had to put a clutch in it around 76K, Mass Air Flow, U joints, new Stereo, Tires, Belt, headlight bushings, valve stem seals, exhaust, (this was my first experience with a C4 and bad cats), and that was about it.
The 90 Nikki has now has been a real trooper. After 150K, it is still stroking. This car has posed some more difficult issues as it has the CCM and other more sophisticated electronics than the 89. I have to admit the computer gremlins have been a headache. On the 90 I have changed, valve stem seals, the idler/a/c bracket, several belts, EGR valve, brake hoses, master cylinder, reconditioned a bent rim, radiator, cooling fans, relays, stereo several times, emergency brake assembly, replaced the entire instrument panel from a donor car, replaced the climate control head, replaced the tilt portion of the steering column as it flat wore out and was flopping around (took me about seven times to get it right), driver side door hinge assembly, several sets of tires, exhaust, Cats, headlight bushings, a/c hoses complete, timing chain (I changed the timing chain trying to solve another problem-turns out it was not bad, but at 120K it did not hurt to put a fresh one in-trying doing that job in the car :bang) We still have a shorted wire in the back up light circuit which is also tied to the blinkers. The only way to get the blinkers to stay working without blowing a fuse was to snip the back up light circuit out. I am sure the wires is rubbing between the fuse panel and back up switch, and it needs a clutch now. The passenger seat power switch burned up years ago, it has a wicked water leak that poors in somewhere behind the dash and soaks the driver floor, and the stereo still comes and goes as it pleases. Several weeks ago the windshield wipers just quit, then they started working again.
So, I don't know how reliable they are, but mechanical stuff is destine to break. If it didn't they would never sell new cars.
Good luck in your search.