P2187 w/ No Symptoms

[cloudguy]

Fully stock 2007 2.3 hatch

Per the tech manual, the most common issues are MAF, O2 and purge valve. Last time I had a P2187 issue the evap purge and fuel pump was replaced under warranty. However, with that issue it was having a rough idle and there were issues after I fueled.

I pulled and cleaned the MAF and the light was off for about 3-4 days but has now returned. It only comes on about 10-15 minutes after the car has been running and is warmed up. When the light comes on there is no symptom. The idle is not really hunting, no vibrations, etc. The problem is intermittent because it does not always come back right away after I clear the code. Since it happens only after the car is warmed up that leads me to think O2 sensor, but I hooked up my bluetooth OBD2 monitor and checked the O2 sensors and the voltage readings all came back fine for now (the problem is intermittent though). Also, the O2 sensors failing usually throw their own specific code.

I have not checked the air box for possible leaks after the MAF yet, and I have not replaced the MAF yet (my initial thought). The car has 170k+ miles (275k km) so I am trying at all costs to avoid having to take it to the dealer and have them run diagnostics and spend big $$$ on a car that is nearing replacement!

Thoughts? My mileage has been slightly poorer recently, but it has also been extremely cold so I chalked some of the reduction up to the weather.

[studum]

You check for vacuum leaks? or exhaust leaks before the 02 sensor?

[cloudguy]

You check for vacuum leaks? or exhaust leaks before the 02 sensor?

Not yet. I was first working under the impression of unmetered air / faulty MAF sensor getting into the engine as the first pass. I will try to use the Torque app and the bluetooth OBD reader to check if there is a vacuum leak also. During normal operation the vacuum reading on the real-time Torque output was within tolerance, but the CEL had not tripped again while I was driving on that trip.

[cloudguy]

I used the fuel trim to check for vacuum leaks at idle. The short term trim was fine, mostly staying positive but oscillating around 0 and never peaking above 15. The long term trim was high though, oscillating around 9.5 but again not high at idle as I would expect with a vacuum leak.

I replaced the MAF and I guess I need to wait for the computer to map the new sensor. The short term trim is doing exactly what I would expect with a leak now, very high at idle (20+) and dropping to close to 0 under throttle. Long term trim is sticking up around 20 right now with the new sensor, not dropping much even under throttle. I will drive it for a few days and see what the readings are again later.