7MGTE Extreme Low Idle and Dies on Throttle - Faulty AFM and Blow-Off Valve Vacuum Leak

Fuel Systemintermediate✓ OP Confirmed

Problem

7MGTE engine in a swap (BMW E30) developed extreme low idle and would die when throttle was applied. The problem recurred multiple times. Engine would not start with the AFM connected, and when started without AFM and then reconnected, idle was erratic and power output was very poor with delayed throttle response.

Extreme low idleEngine dies when throttle is appliedEngine will not start with AFM plugged inErratic idle - sometimes good, sometimes very badVery poor power outputDelay between hitting gas pedal and engine responseEngine runs but will not rev up at all

Root Cause

Two combined issues: a faulty/failing AFM (Air Flow Meter) sending incorrect air volume readings to the ECU, and a vacuum leak caused by the blow-off valve. On the first occurrence, the dashpot adjustment screw was also found loose, contributing to the idle problem.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted October 2014 on SupraForums.com