20R engine in 1979 Celica
I was wondering why the mileage suddenly dropped from 24 to 15(!) mpg, with the engine barely able to idle.
I checked fuel pressure (good), but vacuum was only 15" (it was 20inches last I checked over the summer).
My first thought was a leaking intake manifold gasket. But today, I took the car on a long trip, and when I got into the garage, I heard a squeaking/scraping sound. It sounded like it came from the distributor, Sure enough, if I pressed on the cap, the sound got worse.
So: I removed the cap, and noticed what looked like carbon tracking. Cap was changed 21,000 miles ago. The Toyota FSM says to merely inspect the cap and rotor every 30,000 miles. I change them at 20,000 mi intervals anyway, keeping the old one in the trunk.
Am I looking at distributor problems? There is NO play when I try to shake the rotor shaft from side to side. The only problem it has is that one of the springs for the advance mechanism weights is weak (no longer available from Toyota)
I’m just wondering how a distributor cap could wear out so quickly.
Distributor is original, 247,000 miles