7MGTE Rough Idle and Cylinder Misfires - Loose ECU Ground

Electricalbeginner✓ OP Confirmed

Problem

7MGTE running with rough idle, stumbling and hesitation on acceleration, sounding like it was missing on multiple cylinders. Engine would occasionally die when components near the ECU ground were disturbed.

Rough idle sounding like 2+ cylinders missingStumbling and hesitation on accelerationEngine stalling when components near ECU ground were movedTiming light showed spark loss on cylinder 6 shortly after startingIntermittent code 11 (ECU power/ground fault)

Root Cause

The ECU ground bolt was slightly loose, causing intermittent loss of the ECU ground connection. This caused erratic ignition and fuel injection behavior, mimicking symptoms of bad coil packs or sensor failures. The loose ground was discovered when the owner bumped a nearby VSV and the engine died, leading him to check and find the loose ECU ground bolt.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted June 2020 on SupraForums.com