7MGTE Requires Excessive Timing Advance - Vacuum Leak

7MGTE engine required far more ignition timing advance than normal to run smoothly. The engine wanted way too much timing to run correctly, even though cam timing marks lined up at TDC and base timing could still be set to 10 degrees with a timing light.

A vacuum leak was causing unmetered air to enter the intake, making the engine run lean. The ECU (TCCS) compensated by advancing timing excessively. With the TE2 diagnostic jumper grounded (fixed timing mode), the vacuum leak's effect on timing was masked, but during normal operation the ECU would over-advance timing to compensate for the lean condition.

Moderate confidence — Original poster confirmed this resolved the issue