P0101" and "P0103" which is "Engine misfire cyl#1/3

CLANMAC

MEMBER
1998 SUBARU OUTBACK
4 CYL
AWD
MANUAL
123,000 MILES

For about the last year, when I drive steadily at or above 70mph/3500rpm in 5th gear, the "Check engine" light will come on. Reading out the codes always shows "P0101" and "P0103" which is "Engine misfire cyl#1/3". After a 2 days of driving below this level, the light goes off. It happens in cold and warm, wet and dry weather.

There are no symptoms of roughness, knocking, loss of power nor loss of gas mileage. When accelerating through the gears, the engine pulls smoothly up to 5000rpm. Idle is normal. Switching from 87 octane to 91 octane for several tankfuls made no difference.

Dealer has looked and looked to no avail. Any suggestions?

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

Those codes typically get triggered due to malfunctions within the mass air flow sensor circuit.
They also usually lead to poor idling and performance characteristics.

P0101: Mass air flow sensor circuit range/performance problem (low input)
P0103: Mass air flow sensor circuit high input.

The best course of action would be to take a step-by-step diagnostic approach.
I have attached the trouble shooting procedure for those codes below.
Go through those steps, as that can help determine the issue.

Please let me know if you have any questions.
Thank you.

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