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peterpete190, Auto Technician
Category: Subaru
Satisfied Customers: 27814
Experience:  Auto repair Technician with 17 years experience.Past ASE and other certifications.
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I have a 2008 Subaru Outback. I recently had the car into

Customer Question

I have a 2008 Subaru Outback. I recently had the car into the dealership for its 175,000 mile check up. The car's gas mileage dropped from 24-26 mpg to around 20 mpg prior to my bringing it in. They replaced the spark plugs, changed out the engine air filter, and changed the oil and filters. I drove the car 30-40 minutes on highway and surface streets to my folks and then parked the car. When I started back up I got the CEL. I took it back to the dealership the next day thinking it was related to the service. They looked it over and said they didn't find anything wrong and cleared the code. After receiving the car back I noticed that the car would shudder when I stopped (like it was going to stall out), but then the RPMs would pick back up to normal idle. I drove it back up to my folks and when I restarted the car after being parked the CEL came back on. With the CEL on, the car no longer shudders when coming to a stop. I'm thinking this has to do with one of the O2 sensors, but figured I'd get your thoughts.
JA: Thanks. Can you give me any more details about your issue?
Customer: Car has 176,000 miles as of this morning. This is the first time this car has had this problem and had been running well through 174,000 miles.
JA: OK got it. Last thing — Subaru Mechanics generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.
Category: Subaru
Expert:  peterpete190 replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

With the check engine light on there is at least one fault code set.Since the dealer says there was no code or issues I would have the codes checked/read out by another facility to see what codes are set.You might have a parts store like Auto Zone read out the codes as they usually will free of charge for you.If you can get the codes read out and post the code info here this will help just let me know.

With a studder and if this issue only occurred after the service was done this may be an issue with a damaged spark plug they had replaced as this can occur in some cases here.I have seen this occur before and had to re replace the affected spark plug.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 1 year ago.
Sorry, the dealer was the one who initially ran the diagnostics on the car and pulled the P2097 code. They said the code didn't make sense to them based on the condition of the car/maintenance they just did and, after looking over the catalytic converter and surrounding equipment and finding nothing wrong, they cleared the code so the CEL wouldn't come back on. Would the spark plug issue cause this sort of code to pop up?
Expert:  peterpete190 replied 1 year ago.

Can you tell me what liter engine is in this model here as I see two options including a turbo option?

Customer: replied 1 year ago.
2.5 liter
Customer: replied 1 year ago.
Non turbo
Expert:  peterpete190 replied 1 year ago.

O.k.,this code indicates the fuel trim post converter is to rich on bank 1 side of the engine.The spark plugs usually wont cause this code to set unless the engine is running rough.What can cause this code is the post catalytic converter oxygen sensor reading incorrectly needing replaced or the catalytic converter itself.Usually this code wont be related to the work that was done unless they unplugged the wiring for this oxygen sensor accidentally or damaged the wiring or sensor.Your model has a front cat. and a rear cat.This would be the front cat.

The computer will try and compensate for the rich code by leaning out the fuel supplied to the engine which can cause this studder and near stall out.Since the light did come back on again after it was cleared this will have to be tested/checked into further to see if the oxygen sensor needs replaced or if there is an issue with the catalytic converter itself needing replaced.

Thanks Pete

Customer: replied 1 year ago.
Okay, that is sort of what I expected based on the information I got back from the dealer when they initially checked it out and my previous experience with a Subaru Baja. Thank you for the help.
Expert:  peterpete190 replied 1 year ago.

Your welcome.Let me know if you need anything else and feel free to rate my help here.

Thanks Pete