Spark plug replacement:
Timing chain/tensioner replacement (overview):
Head gasket troubleshooting:
On early models, the distributor shaft seal and camshaft seal leak oil down the back of the engine. Fix: Replace both seals. The cam seal requires timing belt removal. The distributor seal can be done in situ. Toyota 1g Fe Engine Manual
The information above covers 80% of ownership. For the remaining 20% (wiring diagrams, ECU pinouts, transmission mating, etc.), you need the actual PDF manual.
Legitimate sources:
Physical books:
Avoid: Random PDFs on torrent sites—many are for the 1G-EU (carbureted) or 1G-GTE (twin turbo), which are totally different engines.
The 1G-FE is an interference engine. If the timing belt breaks, pistons will strike valves. Bending all 24 valves is almost guaranteed. Consequently, the timing belt section of the manual is the most thumbed.
Recommended interval: Replace every 100,000 km (60,000 miles) or 5 years. Spark plug replacement:
The 1G-FE engine block is iron, but the cylinder head is aluminum. Mixed metals create electrolysis. If you use tap water instead of coolant, the cylinder head will corrode from the inside out.
Manual specifications: