'95 EJ22, poor response/stumble when cold, code P0101 MAF range, advice?

[v8volvo]

I'm driving a 1995 Legacy wagon that I just acquired from relatives from Pittsburgh PA to Seattle WA. Since I picked it up, it's had symptoms of poor driveability when cold. Starts a little bit hard, then idles fine but stumbles badly under load until it warms up. Seems perhaps more severe in damp conditions. These symptoms have been disappearing completely after the car is fully warm, but even then it seems like it might be a little down on power. No MIL for the first 1000 miles I've driven it, but just last night when we were off the highway (engine warm of course) the light came on. Pulled codes and found a P0101 MAF Range Error stored.

 

Are the MAF sensors a common source of trouble on these? I searched and found a couple discussions about this code but not enough to make me think it is a regular problem area, and those threads were somewhat inconclusive as to what the fix was. One mentioned that the MAF's in these respond well to cleaning. I have a new air filter on board and could put one of those in, along with cleaning the MAF with appropriate CRC product. Recommend giving this a try? Or more likely that it just needs to have the sensor replaced?

 

I had initially thought that it probably needed a general tune-up to sort out the cold running issues, but now I wonder if the MAF has been the issue all along. The theory I'm working on is that what is going on is the MAF is feeding the ECU a faulty signal (probably low), which makes it run poorly when cold and in open loop due to incorrect fuel mix, and then once it warms up enough for the O2 sensor to come online and the system goes closed loop, the O2's feedback allows the ECU to correct the fuel mix and compensate for the incorrect MAF signal. Sound like a plausible explanation?

 

Next move? Try cleaning sensor? Replace? Keep driving and hope it doesn't recur?

[MilesFox]

I would suggest the coolant temperature sensor as a more common occurrence, especially that the car behaves differently cold than warm.

[v8volvo]

Confirmed CTS is measuring coolant temp accurately when warm per live data accessed with scanner. Still need to check it when cold but suspect it is working OK. Perhaps the poor cold power delivery is just due to tune components in poor shape. Will be able to check that out when I get it back home and have access to tools. Not too likely a CTS fault would result in a MAF error code, I think, no?

 

In the meantime, I've cleaned the MAF sensor element with appropriate cleaner, replaced cheap Chinese filter element with OEM Subaru, and cleared the MAF error code. No recurrence of code or illumination of light since then, in 1000 miles of driving over the past two days. Now in Kansas City, MO and running fine. Still a little rocky when cold but seems better than it was. Figuring unless obvious issues arise again, or someone smarter than me on here suggests otherwise, I will get it home to Seattle (halfway there now) and deal with it then.

 

Thanks for the advice.