Having problems with your 2008 Subaru Outback ?

Low power at low RPM before turbo starts working. Difficult to drive the car on mountain roads where you have to shift from third to second gear, often the engine is not capable ot takes long time to rise in rpm enough to allow the turbo to start.

Posted / edited by AnonymousUser on : 22-04-2019

Answers :

Hi Mirezza.

The IACV is idle air control valve. The function of this part is adjusting amount of air being mixed with fuel when the engine is idle. If that is the problem, the engine will turn off when revving very low (idle). If problem happens in third gear, it is unlikely IACV.

There are more problem that can cause engine turning off at low RPM.

To start try to understand if problem is misfire, fuel, or an automatic transmission shifting the wrong gear. If problem is misfire one of the cylinders won't fire, you can feel and hear the engine going bad and vibrating in the wrong way.
If problem is transmission (auto only) you can notice that the gear is wrong. I think that you are talking about a manual transmission by the way.

The problem is more likely fuel/injection.

Either there is not enough fuel being injected, or the air/fuel mixture being injected is in the wrong proportions.

The first thing I would do is a DTC code scanning using an OBDII reader (e.g. U380). The scan can be done for free at Autozone (in USA only), or for a small fee at the dealer or at any qualified garage. If there are codes stored this can address the problem.

In presence of no codes there are several defects that result in engine turning off.

dirty injectors will spray insufficient fuel. Try doing an injector cleaning. Injectors can be tested using a noid light and doing a spray test.

Vacuum system.
The vacuum system has different functions. A vacuum leak will cause a number of problems and sometimes returns a 'lean' dtc when scanning codes. Big vacuum leaks or open vacuum hoses can be spotted at a glance. To find small one you use a gauge like this: Gauge Tester in the vacuum lines while spraying carb.cleaner on the hose. The spray will temporarily close the small leak and pressure will go up on the gauge.

Fuel pump:
If fuel pump or pressure regulator is bad you get incorrect pressure, and this can cause your situation. The turbo kicking in may cover the problem with engine running at higher rpm.
To test pump and regulator you use the same gauge for the vacuum. Connect the gauge to the port on the fuel rail, and observe pressure with engine running and after turning on (check psi drop to test pressure regulator). Here a summary description of the test: How to Check for...
Replace also fuel filter.

Air intake and sensors:
This determine the amount of air being mixed with fuel. Clean MAF sensor and replace air filter. If problem happens only when engine is cold, check also the IAT sensor.

EGR valve:
This is a valve connected to vacuum system. Its role is opening and closing to recirculate gases from exhaust. If it is stuck closed or malfunctioning the engine will run rough.

Problems such as bad head gasket may result in low compression. In that case the engine produces less power than normal.

There are more failures that result in the symptoms you described, I listed the most common faults. Do a DTC code reading and test the above. You will be probably able to spot the problem.



Hi, the transmission is slipping Or your fuel filter is simply clogged up and starving the engine of fuel, clogged fuel injectors? dirty IACV? sounds like your car is starving from something...

You can alsotry to clean your throttle........
Repair Help & Product Troubleshooting for 2008 Subaru Outback

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