Ok, I've been driving my 83 TD Rabbit for a couple months now, and have two primary issues- I can only access about 9.5 gallons of fuel in the tank, and the mileage is bad. Like the highest I've seen is high 30s bad. It's even been in the high 20s.
I know the turbo is trashed, it howls and barely makes boost, as soon as it starts spooling the black smoke comes on even at half throttle. Today I ran about 300 miles (used the whole tank), and it didn't have much love for exceeding 60. I checked the boot from the turbo to the intake and it is intact without leaks. The air filter is clean, and the airbox is unrestricted.
I plan on replacing the turbo on Saturday, and make sure the wastegate is actually working, but I get the feeling this isn't 100% of the issue. I am also looking at doing an in-frame overhaul, as the crank has significantly more end play than I find acceptable, and there does seem to be some blowby- How much do the cylinders usually wear in these engines? It has 140k, is it typical to get away with stock bore stuff and hone the cylinders, or do they wear a bit? I ask because I did the head gaskets in my Alfa at 240k and the bores were perfect, still had excellent crosshatch and that is typical for those engines.
The car had the timing belt replaced a couple years back, is it possible for improper cam timing to cause poor mileage but decent runability?
A previous owner left a bit of a story on the car's early life in the glovebox, stating it spent a fair bit of time cruising I5 getting 55mpg, I'd be thrilled if I could even hit the mid to high 40s.