Cylinder 1 Running Rich / Fouling Plugs - Cold Start Injector Temp Sensor, Fuel Pressure & Timing

Fuel Systemintermediate✓ OP Confirmed

Problem

Cylinder 1 running extremely rich on a 7MGTE with 550cc injectors and HKS piggyback ECU, fouling spark plugs within 10 miles of driving. Could not tune out the rich condition with GCC or VPC adjustments. Initially suspected a leaking injector.

Cylinder 1 spark plug fouling within 10 miles of drivingExtremely rich condition on cylinder 1 onlyMisfire on cylinder 1 after short drivesUnable to tune out rich condition with GCC or VPCCylinders 2-6 looked fine, only cylinder 1 affected

Root Cause

Combination of three issues: a broken cold start injector (CSI) temperature sensor on the thermostat housing (plug was totally broken away from the probe), fuel pressure set a few PSI too high for the 550cc injectors, and ignition timing slightly off. Swapping injectors 1 and 6 confirmed the problem was NOT a leaking injector since the rich condition stayed on cylinder 1.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted April 2023 on SupraForums.com