About this project

The truck and the swap

A 1988 Toyota 4Runner is getting a rebuilt, supercharged 3.4 L 5VZ-FE from a 1998 4Runner in place of its original 3.0 L 3VZ-E. The truck keeps its R150 5-speed and its 88 gauge cluster. The engine gets a Magnuson MP62 supercharger, a CS144 alternator, bluetop injectors and a custom exhaust.

Bolting the engine in is the easy part. The hard part is that the two trucks are ten years apart. The 1988 truck was built around an OBD-I engine computer and a 1980s body harness. The 1998 engine expects an OBD-II computer, different sensors, different relays and different plugs. This repo is the working record of making those two systems talk to each other, and of rebuilding the engine itself.

What the repo is

It started as a folder of notes and turned into a small, organized engineering project:

• Research write-ups (research/): one question per file. Power budget, gauges and speed signal, every plug on the 98 engine harness, a full audit of the wiring plan against the factory manuals, sealant alternatives, and engine bolt sizes.
• Wiring data (research/pins98.json): the pin tables for the 98 engine computer and harness plugs. The connector diagrams and plug lists are generated from it, so they never drift apart.
• Generator scripts (tools/): Python that turns the notes and pin data into printable pages: connector diagrams with photos of the actual plugs, the plug-by-plug harness list, the build binder, and this website.
• Working logs: a cut log for the old harness (every wire beeped before it was cut), a meter-check list in build order, and a to-do log that records each decision with its date.
• Printable pages (print/): sheets taken to the garage and filled in by hand.

How the information was checked

• Factory manual first. Torque specs, wire colors and pin numbers come from the Toyota factory service manuals (1998 RM580U and EWD319U). Each one cites its manual page code, such as EM-56 or DI-158. The manuals themselves aren't published here; they're Toyota's.
• Audited, not trusted. The engine-build guide was checked line by line against the manual. Each line is marked MATCH, FIX or OMISSION, and the fixes were applied. Community wiring write-ups were checked pin by pin against the T100 manuals before any of their tables were used.
• Measured on the truck. Every 88 pin used in the plan was confirmed with a meter on this truck before the plan relied on it.
• Open questions stay visible. Anything not confirmed is marked UNVERIFIED in the notes rather than smoothed over.

How it was built

The research, cross-checking, writing and code were done with Claude Code, an AI coding assistant, working in this repo. I drove the decisions, did the physical work, and took the measurements. The assistant read the manuals, kept the notes consistent, and wrote the generators and this site.

This website

• Generated, not hand-written: tools/build_site.py reads the same Markdown notes and pages the build uses and writes a static site, so the website and the garage binder can't disagree.
• Privacy check: the build refuses to finish if any private detail or factory-manual file would be published.
• Hosting: Cloudflare Pages, with one small Pages Function and a KV store holding the checklist progress. Anyone can read the progress; only I can change it, behind Cloudflare Access.

Credits

• theMonch: the 5VZ-FE into 88 4Runner wiring write-up that started the wiring plan.
• ORS: their 5VZ conversion guide, crossover and header kits.
• Magnuson: the MP62 kit and its install manual.
• The YotaTech community: years of swap threads.

This is a record of one truck's build, not a how-to. If you're doing your own swap, verify every spec against your own factory manual.