Oil control valves on avcs/dual avcs equipped subarus

Oil control valves are nothing terribly new to the variable timing community. To Honda, they're called "VTEC solenoids". In truth, this part does the exact same thing on all cars equipped with variable timing. They provide extra oiling when needed to the cams on demand. An unfortunate downside is that this is a part that is designed to fail. There's no getting around this despite what a few of the budget minded folks tell you. This is also a good thing as the stuff that causes them to fail over time is prevented from destroying your cams. This can be argued, but I'm not going to go into those points in this discussion.

What I am going to go into is that this is a part that should be but isn't part of a periodic maintenance plan. Right around the 70k mark, these tend to fail. Failure tends to mimic head gasket failure without overheating and excess smoke. The car will run rather rough and will show low compression on one side of the engine. The driver's side usually is the first to fail, but the passenger side can also fail. The car will also throw a code that does not necessarily correspond to the oil control valves in spite of the ecu having DTC's for them. Early symptoms of a failing valve are sporadic moments of low power/hesitation, like the car is not getting enough fuel or spark. Reason for this is bacause the ecu is cutting spark to that side of the engine to prevent you from killing your motor due to inadequate oiling to teh cylinder head.

Because of this, it's not too uncommon for some dealers to take advantage of this and try to play the issue off as a head gasket failure, which costs $2100+ and takes a fair amount of time rather than an oil control valve replacement which cost's about $300 for one and takes 10-20 minutes to complete (you can replace both yourself for about $300.

Now a few people will tell you that you can simply clean them periodically and not ever have the issue. This both is and isn't true. In truth, all you are doing is prolonging failure because unfortunately this is a part that is designed to eventually fail. An apt comparison is a water pump. An oil control valve is not designed to be repaired. Hovever, because of their design, they are relatively cheap. Additionally, the good folks at Subaru made them extremely easy to get to.

Now I bring this up because this is one of those parts that's not in your Haynes and Chiltons. You'll only find them in an Subaru Service manual. But even there you won't find them as a maintenance item, but as a repair/replacement item for when they fail. They really should be part of the periodic maintenance due to the failure rate.

So what's the solution to them? Replace them periodically. 70K is really the earliest you should do it. To me, it's also the latest. If you were to ask me, I'd simply replace both at 70k rather than replace one when it fails and hope that the other one doesn't.

Jon