|
Just had a thought.
When was the pre cat o2 sensor replaced? (recommended every 100k, or 85k in my case)
The DME detects misfires by looking at this sensors AFR reading on a per cylinder basis.
So if it detects rich pulse at the same time as these cylinders plugs are firing, it will log a misfire (unburned fuel causing a low AFR reading)
Perhaps it is the sensor that is sending an incorrect AFR reading - just out of spec enough to cause a misfire code, but not enough to be logged a faulty (because the other two cylinders are not misfiring)
If the DME sees a low AFR it will reduce the fuel quantity causing a weak misfire.
Might be worth changing it as its an easy job if you have a 22mm sensor socket.
|