Misfires, low power 06 V70

[rswearing]

2006 V70 2.5T. 275K miles.

Has started misfiring, engine loses power, mileage is in the dumpster. Problem doesn't start until after engine has run for a while, and usually not unless I put it under a load like accelerating into traffic. If I turn the engine off and restart, problem goes away for a bit. Check engine light is on and Engine Service Required message displays.

Replaced the ECT sensor.


Codes indicate
P0300 - Random Misfire Detected
P0301 - Cylinder 1 Misfire Detected
P0302 - Cylinder 2 Misfire Detected
P0101 - Mass or Volume Air Flow Circuit Range/Performance
P0170 - Fuel Trim Bank

I cleaned the MAF sensor when I replaced the ECT. I'm thinking the MAF is bad, but before I spend money on one and install it, I'm hoping for some more experienced opinions. I'd hate to spend 130 on a MAF when $30 of sparkplugs would have done the job.

Coils? Sparkplugs? The pipe leading from the PCV vent is cracked and leaks vapor when the engine is running...don't think that would cause a misfire though.

[abscate]

Definitely pull plugs and check, and move your number 1,2 coils to new cylinders to see if the codes move.

IF there are over 100k miles on the coils, get some new ones in. Check the date codes - I hope they arent 2006...

[rswearing]

Why the MAF code then? I get that a bad MAF could cause the misfire code, but can a misfire from a bad plug/coil cause a bad MAF code?

[RickHaleParker]

Have you tried clearing the codes and see which ones come back?

P0101
Check for air leaks in the air intake system, any holes in the plumbing?
Check for restricted air flow, how dirty is the air filter?
Contacts to the MAF clean and in good shape?

Possible source

• Contact resistance or oxidation in the mass air flow (MAF) connectors
  Air leakage in the intake system
  Blocked intake system
  Damaged mass air flow (MAF) sensor.