We're talking about a 2005 Volvo S80 2.5T 5-cyl engine vehicle here. Back in late September was the first time I experienced this engine shudder/stutter behavior when the tachometer dial went from say something around 2k RPM and dropped to round idle near 600RPM or so. The engine would be firing smoothly and then as the needle dropped near idle the engine bay would shake and the needle would surge up slightly and then fall to idle and things would rapidly settle after about 1 second of shudder.
I was in traffic on the highway today and decelerating as I approached a stopped car where my RPMs dropped and then I got into this stutter/shudder surge loop where the engine would shudder, then surge, then shudder then surge, something like 2-3s spacing between each for a total of like 3-4 rounds. When I got home I revved up the engine while parked and let it fall again and found the shudder was pretty reproducible. As the shudder occurred I noticed the headlights grew dim then recovered as the shudder left. I let the car rest for like 30 min and went back to move it to the carport and the same shudder occurred as the RPMs dropped.
I scanned my car and got two pending codes listed, the same as those that occurred in September:
P0101 Mass or Volume Air Flow Sensor "A" Circuit Range/Performance P2188 System Too Rich at Idle Bank 1
I recorded about a minute of live data during about 5 or 6 engine revs. What PIDs should I inspect to gain some insight into what may be wrong?
I have the following PIDs recorded
Time (s) Engine Coolant Temperature (Â°F) Catalyst Temperature Bank 1 - Sensor 1 (Â°C) Absolute Throttle Position B (%) O2 Bank 1 - Sensor 2 - Oxygen Sensor Voltage (V) Barometric Pressure (kPa) Fuel Pressure (Gauge) (PSI) Vehicle Speed (MPH) Absolute Load Value (%) Wide Range O2S: Bank 1 - Sensor 1 - Equivalence Ratio (Î») Ambient Air Temperature (Â°C) Long Term Fuel Trim Bank 1 (%) Commanded Throttle Actuator (%) Timing Advance for #1 cylinder (Â°) Accelerator Pedal Position E (%) Short Term Fuel Trim Bank 1 (%) Wide Range O2S: Bank 1 - Sensor 1 - Current (mA) O2 Bank 1 - Sensor 2 - Short Term Fuel Trim (%) Calculated Engine Load Value (%) Accelerator Pedal Position D (%) Engine RPM (rpm) Mass Air Flow Rate (g/s) Relative Throttle Position (%) Control Module Voltage (V) Intake Air Temperature (Â°C) Absolute Throttle Position (%)
What exactly could cause this combination of DTCs? How should I approach diagnosing this set of symptoms? Also what sort of risks are possible driving in this condition? Could a failing MAF stall the car while driving or anything like that?
EDIT: checked on the wiring voltages this morning, everything seemed as expected more or less
- 12V source
- 0V Ground -- shows continuity with battery ground
- 0V ?? -- no continuity with battery ground