Skip the auto shop - Our mechanics make house calls

Q: I have a 2003 Subaru Forester and upon starting this morning it ran fine for a minute or two. Then the Check Engine Light came on.

asked by on

I started my car this morning and it ran fine for a couple minutes. Then as I went to put it in gear the check engine light came on and it started running rough.I was told that it's possibly a pcv problem

My car has 209537 miles.
My car has an automatic transmission.

Too much air flowing into the intake causes the engine to lean out too much air in relation to the fuel and misfire. At an idle, the PCV valve restricts air flow, to reduce this problem. At high manifold vacuum (idle), a spring loaded valve is drawn up and partially restricts flow to the crankcase. The PCV system is relatively simple. An inlet hose connects to a filtered air source. This is used to supply clean air that is drawn through the engine. Most of the time this air is supplied through the engine air filter.

On a few designs there is a separate inlet filter that cleans the incoming air for the PCV system only. This filtered air flows through the engine, picking up fumes and vapors. The air exits through another hose, connected to manifold vacuum. The flow of air draws fumes from the crankcase and burns them harmlessly in the engine. This also creates a slight vacuum, relieving any pressure that may build. Negative pressure helps to prevent oil leaks and oil consumption by the engine. The PCV valve also helps regulate the amount of air flow, which helps prevent oil being drawn out of the engine. When the PCV valve is not working correctly, this will cause an imbalance in air flow and vacuum causing the Check Engine Light to come on.

I would recommend having an expert from YourMechanic come to your location to diagnose your Check Engine Light firsthand and replace your PCV valve as necessary. Best of luck.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. I have a 2003 Subaru Forester and upon starting this morning it ran fine for a minute or two. Then the Check Engine Light came on.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Including parts and labor, what is the cost of replacing the serpentine drive belt on a 2009 Subaru forester with 83,000 miles.

The service life for a modern serpentine belt is typically around 100,000 miles so long as the belt has been properly tensioned and has not been exposed to contaminants such as oil, grease and anti-freeze. Belt life also depends on...

Q: Car lacks power

First check your EGR system for leaks. If EGR is on or stuck, at idle, that can cause rough operation. To further diagnose your issue, obtain compression test results (in case the issue is due, even in part, to burned...

Q: My car won't accelerate in drive. But will accelerate in park or reverse. The last couple of days. While driving the battery ligh

You may have a defective transmission valve body or the transaxle is bad internally. The manufacturer recommends replacing the valve body assembly first and then the complete transaxle if the problem is still happening. I suggest having you transmission tested...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.