One of the most common issues your Subaru Forester is likely to develop is a stalling problem. The most challenging part of diagnosing a stalling problem is reproducing the conditions that led to the stall in the first place. Stalls can happen at any time, and it can be incredibly jarring when it does happen.
Before troubleshooting any automotive issue, including stalling issues with the Forester, make sure that you check the vehicles trouble codes with an OBD2 scanner. Trouble codes are always a great place to start diagnosing problems on today’s modern computer controlled vehicles. Without them, you are in the dark.
These codes are vital to diagnosis. They are often specific enough to get you all the way to the problem, or pretty darn near. If you don’t own/want to buy a scanner, most local parts stores will run a scan for you at no cost (they want to sell you the parts).
Subaru Forester Stalling Problem Causes
Here are some of the issues that cause the Forester to stall out. Remember, a vehicle needs air, fuel, and spark to run. It needs them in the right quantities and intervals, or it won’t run right.
Fuel
Fuel issues are one of the most common reasons that a vehicle would stall out, that includes your Subaru Forester.
- Bad gas- can cause an engine to stall out. Water in the gas tank can also cause gas to not fire properly. If there were no other symptoms and suddenly you find that the vehicle is running very rough, bad gas could certainly be the problem. Here’s a good article on all the symptoms of bad gas.
- Air Fuel Mixture– If the air/fuel mixture is off, your Forester can stall out. Usually it’ll be a bad sensor reading, vacuum leak, or other problem that’ll cause the air/fuel mixture to be wrong.
- Bad Fuel Injectors– If the fuel injection system is allowing too much or too little fuel into the combustion chamber, than your Forester will stall out. Or, it just may not be able to properly atomize the fuel anymore. Here’s more on Subaru Forester bad fuel injector diagnosis.
- Not Enough Fuel– The fuel pump may not be able to provide the fuel pressure needed for the engine to run properly. When it asks for a lot of fuel, instead of taking off, it stalls out with the demand. This can be caused by the fuel pump or fuel filter.
Engine Timing
If your Subaru Forester’s engine timing is off, it’s going to stall out, misfire, and altogether not run properly. Here are some of the more common causes of an engine timing problem:
- VVT Problem– Many modern engines are equipped with Variable Valve Timing. This allows for the engine to be in the “sweet spot” of power or economy depending on how hard you are pushing the gas pedal. If there is a VVT issue, it’ll often throw trouble P0010, P0011, or other related trouble codes. This is often the cause of the stalling.
- Timing Chain Jumped– If your timing has jumped a tooth or two, it’ll definitely stall out. Just know, that if it jumped a tooth, it’s only a matter of time before it jumps more or breaks all of the way. If that happens you are going to go from misfire to un-drivable. Here’s more on timing chain jumped symptoms.
Sensor Issues
Your Subaru Forester uses a series of complex sensors to report what is going on to the ECU. The ECU then uses this information to adjust the timing, air fuel mixture, and more. When one of them goes wrong, it can lead to stalling for sure.
- Throttle Position Sensor– The throttle position sensor is typically located on the gas pedal. This sensor is responsible for telling the engine how much air and fuel to allow in. It is very rare these days to be actually directly controlling the amount of fuel and air entering the engine directly. These days the computer handles all of that. This serves two purposes. The first is that by limiting the amount of torque when you push the gas pedal for a second or two, engine life is increased by reducing the stress on it during takeoff. The second is improved fuel economy. Here’s a great article on diagnosing a bad throttle position sensor from cars direct.
- MAF/MAP Sensors– These sensors are responsible for air measurement. When they go bad, your Forester may not be letting in the right amount of air for a quality air/fuel mixture. Here’s more on diagnosing a bad mass airflow sensor.
- Oxygen Sensor– The oxygen sensors measure the exhaust gasses after they exit the combustion chamber. The ECU uses this data to make adjustments to the air/fuel mixture. If one of them has gone bad, then it could lead to stalling.
There are many other sensors that can cause your Forester to stall. These were just some of the most common ones.
Dirty Throttle Body
A dirty throttle body can lead to stalling in your Forester. If you let off of the gas coming to a stoplight and it stalls for a second or two and recovers itself, it very well could be a dirty throttle body that is causing the problem. Here’s a great YouTube video from EricTheCarGuy. on how to clean a throttle body.
A dirty throttle body may not trigger the check engine light. So, if your stalling happens when coming to a stop, and the check engine light is on, it may be worth taking a look at it.
Torque Converter
All modern torque converters “lock”. What this locking does is provide a true mechanical connection from the engine to the wheels. This eliminates some driveline power loss and improves fuel mileage. If the converter doesn’t unlock, then the engine will stall much like a manual vehicle does when it doesn’t have enough speed to carry a gear. It’ll often throw code P0740.
Oil Consumption
If there is almost no oil left at all, the engine could be on its way to locking up. It’s worth a look, especially if you can’t remember the last time that you checked.
Conclusion: Subaru Forester Stalling Diagnosis
As you can see above, there are many different reasons that your Forester could be stalling. Please, please have your trouble codes read if there is a check engine light on at all. It can really help narrow down what you need to do. If there is anything that you would like to add, please drop a comment. Good luck!