Problem: The customer complained that the car
had no power and poor acceleration primarily in the mornings when
it was cold.
Details: The technician verified the low power,
poor throttle response and slow acceleration during cold engine
No DTCs were set – when the engine reached normal operating
temperature, it ran normally.
The catalytic converter had already been replaced and the
muffler and resonator were original.
The technician pulled the front O2 Sensor to install an
exhaust back pressure gauge. Test results were good – 2.8 psi at
Long Term Fuel Trim while cruising and during heavy
acceleration was staying at +16%.
Confirmed Repair: On recommendation of the
Tech-Assist consultant, the technician disconnected the Mass Air
Flow (MAF) and the Long Term Fuel Trim slowly dropped to
zero. He replaced the MAF sensor and the engine ran