2000 OBW. 
150k

Codes: P0172 (System Too Rich), P0301, P0302, P0303, P0304 (Cylinder 1-4 Misfire Detected). These all pop at the same time if I were to clear the codes. Car runs fine otherwise.
 

I've had this check engine light for about a little over a year but within the last few months it began flashing at me. At first it would only flash when driving away without the engine being fully warmed. Now it occurs more frequently, warm or cold. Seems to run okay throughout. I don't notice any change in performance otherwise (slightly lower MPG's but that could be the winter blends).

Some things I've done myself to troubleshoot: 

• New plugs and wires (NGK on both. Blue Subaru wires), Plugs twice in the last year thinking it had something to do with the G-type NGK plugs. Went back to conventional. No change
• swapped coils with known-good coil
• changed fuel filter (the one by the brake booster)
• replaced dried vacuum lines
• vacuum leak smoke check
• running vacuum check (seemed okay) my gage has a green section on the dial that's supposed to be "normal". It was within that.
• replace A/F sensor (OEM from Subaru dealer) last year when the light first came on. Ran okay for a few weeks, then misfire codes came back
• ordered another one as a shotgun approach but I doubt that will fix it since the last one is only a year old.

I use an OBD WiFi dongle and an iPhone app to check/clear codes but they're pretty basic.

I'm at a loss now and don't know what else to check. 

Figured I'd check in with you all before I throw in the towel. 

Side question:
Can this year Subaru send other CAN messages to the right OBD reader? Like fuel trims, etc. 
My thoughts are if I take it in to a well-equipped mechanic they can use a more sophisticated scan tool to diagnose more thoroughly than I can with my OBD dongle.

 

 

Coolant Temp Sensor.  

3 hours ago, lmdew said:

Coolant Temp Sensor.  

That crossed my mind too. 

Cheers 

Bennie

I replaced the temp sensor with a dealer part. 
no change whatsoever. 

Any other suggestions before throwing in the towel?

vac line from fuel pressure regulator dry?

On 1/12/2022 at 1:57 PM, 1 Lucky Texan said:

vac line from fuel pressure regulator dry?

Replaced all the dry crusty vac lines already, including the lines going to the regulator.
Did a pressurized smoke check as well. Other than slight leakage around the air filter box (where the two halves clip together) everything checked out alright. 

Edited January 13, 20224 yr by 211

thoroughly check the air intake.. make sure there are no blockages, debris..
also, how old is the air filter?

Air filter is cheap - change it.

17 hours ago, 211 said:

Replaced all the dry crusty vac lines already, including the lines going to the regulator.
Did a pressurized smoke check as well. Other than slight leakage around the air filter box (where the two halves clip together) everything checked out alright. 

 

check inside the new line for fuel. The FPR's diaphragm inside can leak fuel.

PCV valve. Are you burning oil?

 

One clue? "replace A/F sensor (OEM from Subaru dealer) last year when the light first came on. Ran okay for a few weeks, then misfire codes came back"

So, the o2 DID fix it, if only temporarily???? This probably means something to a  Mech/Tech expert.

- Fuel injectors...check resistance. I don't know what it should be for your year...those are Top-feeds, correct? No, it's not likely that all 4 are bad.

Cause of P0172:

• Faulty fuel injectors leaking fuel into the combustion chamber
• Faulty spark plugs
• Faulty manifold absolute pressure sensor (MAP)
• Faulty throttle position sensor
• Dirty or clogged air filter
• Vacuum leak
• Faulty ECU (or PCM module)
• Faulty fuel pressure regulator
• Faulty thermostat (stuck open)
• Cooling system that’s been retrofitted (ie: thermostat removed, fan running direct, etc.)
• Restricted or damaged fuel line

 

FWIW:

If 'throwing in the towel' means selling for a loss....then how much is it worth to have a Reputable Subaru Shop (not a dealer) check it out?

Drop a $200 for a diagnosis>>fix vs. lose $1K or more because the CEL is on? 

Of course you live in the PNW, so Subaru Central..... peeps probably come up to you on the street with offers...plus the overpriced PandeMarket.