To be or not to be......
 

I purchased a 1990 C4 with 85k on the clock that has been sitting for several years. It is cosmetically in good shape, but its a project car. I am wrestling with myself whether to go forward or bail, mostly because the Porsche Master Tech and the Service Manager at the dealership where I work both tell me to run the other way, and fast. I do realize that this is a model with more than average share of issues, even without the neglect that this one has had. But is it reasonable to think that a mechanically average (i.e., not trained, ect.) enthusiast can resurrect and maintain such a car without total exasperation? Thoughts and comments appreciated..........

Depends on the issues you're facing; what do you know to be wrong with the car?

Things known
 

Engine may need to be rebuilt. Leaks oil like a sieve, and was taken to a shop in'08 because it wouldn't start. A leak down test was performed but could not find the results. Cannot run the engine because shaft key way on generator stripped and cannot fit with new belts for generator and cooling fan. Anticipate at least a mild rebuild. Front diff seals bad; sunroof, windows and driver seat non function electrically. Steering rack boots shot, dont know if rack will need more. Suspect a/c will need refurb. Brakes and clutch likely good.

Do you have tools, a good workspace, time, and a budget? What do you have into the car now?

At 85k the engine is unlikely to need a rebuild unless it wasn't cared for; finding unopened examples with twice the miles isn't difficult. The oil leaks are common and while "like a sieve" is relative (are you used to Hondas or Alfas?) many serious leaks can be addresses while the engine is in the car.

A rebuilt alternator isn't huge money and is relatively easy to do provided you have tools/time/workspace.

Front diff seals are very easy (given t/t/ws).

The sunroof may be a PITA, but the windows and seat are well known in the user community and some tinkering/parts replacement should fix them.

Rack boots/reseal are common issues and relatively easy to deal with given the above.

AC has a number of expensive parts which will probably require replacement; the compressor can be rebuilt with inexpensive parts, but the heat exchangers may need new and the evaporator is buried in the HVAC system behind the fuel tank and is a PITA to get after.

Then there's the emotional issues.... Is a C4 what you want? In my case it was, so I'm willing to deal with the additional complexity (it's amazing in loose conditions). If you're only looking for a fair weather driver you may be better served by a 3.2 Carrera or 3.0 SC.

The 964 is gaining in popularity and prices are rising. You could look at that as either an opportunity to get out from under or as an opportunity to become custodian of that rare beast, the appreciating automobile.

Luck!

The engine, while more complex than its predecessors, is still a 911 engine. You can rebuild it if

a) you are willing to invest a lot of money in the proper tools for the rebuild
b) you are willing to do extensive research, both with the factory documentation and this and other websites, about how to do it correctly;
c) you have the ability to follow directions and manage a complex, multi-month project involving outsourced suppliers; and
d) you have a workspace that is suitable and clean, and you work clean.

Most people in the Porsche world have the above attributes. Some have those attributes to an extreme, almost pathological level.

The big thing I would worry about is the AWD system. The 964 was the early, more complicated version. I remember an article in Panorama by Paul Reiser basically saying that the cost of certain replacement parts in the system was greater than the value of the car.
That is what I would be worried about, not the opinions of folks at the dealer who in all likelihood are more accustomed to modern cars.

Suggestion: Buy a copy of Wayne Dempsey's How To Rebuild and Modify Porsche 911 Engines and see what is involved in the basic 911 rebuild. The 964 is different to be sure, but not so much different-- after reading that through you will be more able to make a decision.

Good luck!