My first post here so please bear with me but pretty desperate for help. Have 2004 Boxster S and its, in general, running a bit rough (feels fuel rich). It also will also, on occasion, not go. Pulling up at a busy intersection and car reduces to Idle. Then put the foot down and the car stays at idle. Normally an engine restart gets things going again (although not always and sometimes requires a few goes).
Bought a computer reader and found error codes
P0102: Factory Fault code 115 - Mass air flow sensor - below limit
P2135: Accelerator Pedal - Signal Implausible
P0121: Factor Fault code 117 - Throttle value or accelerator pedal potentiometer - signal implausible
P1266: Factory Fault Code 409 - Fuel shutoff function monitor - signal implausible
Took the car to Porsche. They suggest a MAF sensor was the root cause and replaced it. It felt better for a few days then problem returned. They replaced another MAF sensor.. Same problem. They then said the MAF reads 0 and have checked the cables so its me DME and it needs replacing (not cheap)
Have taken the car back home and looked at the likely affecting values myself from the computer.
The computer shows to different values for MAF
Mass air flow (HFM) is always 0 regardless of if the car is working correctly or not and at any accelerator level
Mass air flow seems to move within a range of 18 (idle) to 100 (full throttle)
2. Throttle (since it had error codes on this)
Pedal encoder potentiometer 1 and 2 always move and the pedal value goes from 0-100% when its working but stays at 0 when its not. Since the potentiometers always move I am assuming the DME simply can't add things up so sticks the pedal value at 0.
ie. The MAF sensor reading above confuses the DME and it reduces the throttle to 0. That feel consistent with the behaviour of the car (its just sticks at idle)
Any one with any clues? Certainly don't want to replace the DME unless absolutely necessary....