A good understanding of the variable valve timing (VVT) solenoid and oil control valve (OCV) can help to understand its history and some of the impact it has on the performance of our cars, SUVs, and light trucks.
Variable valve timing solenoids (oil control valves) are important to the performance and efficiency of the engine. VVT solenoids will enhance performance by optimizing the opening and closing of the valves and improving power output and fuel efficiency. They unfortunately only provide this benefit for a limited time before failure.
Let’s take a look at commonly found symptoms of a failed oil control valve, what can cause such a failure, and how much it can cost to replace a VVT solenoid.
The engine has valves that control the flow of air, fuel and exhaust gases through the combustion chamber. The valves are activated open and closed by a camshaft mechanism.
There could be upwards of four camshafts depending on the engine configuration in your vehicle, and they typically use a chain or belt that is driven from the engine crankshaft.
The cams of decades past had a fixed pattern of valve opening and valve closing with respect to the position of the pistons.
This was called valve timing, and it was entirely pre-determined by the manufacturer and built into the engine. Valve timing was done to obtain maximum performance but allow for acceptable fuel economy.
Variable Cam Timing
Variable cam timing (VCT) was next. This introduced cam timing that varied over a set period of valve function.
Engine patents for these systems date back to the 1920s and engineers were able to conclude that variable valve function during change in engine speed may have the advantages of performance and fuel economy.
Alfa Romeo was the first manufacturer of variable cam timing on a production car. This came standard on the 2.0L fuel-injected engine in the 1980 Spider. This was uncomplicated design which offered intake valve retardation as engine speed increased.
The result of this mechanism was the addition of mid-range power. Just by this one feature, it was a great benefit to this small Alfa engine.
As it turned out the concept of variable cam timing started to catch on. That was in 1989 when Honda was the first manufacturer to employ theirs in the VTEC engines.
Porsche introduced theirs in the VarioCam in their V8-powered 928 models. Variable cam timing has taken off a bit since then and can be found in motorcycle engines as early as the early 2000s.
As recently as 2016, Borg Warner designed a VCT for the 2016 Hyundai Lambda II engine series. Borg Warner VCT included the first ever cam mid-position lock allowing the cams to hold a center setting when advance or retard was not needed.
You will now find virtually every auto maker is on the VCT train. In addition to performance and fuel economy advantages, it’s also found to assist in reducing vehicle emissions like oxides of nitrogen.
What is an Oil Control Valve (and How Does It Work?)
In most current Automobiles engine’s valve timing is accomplished via cam control mechanisms that change cam position relative to the engine crankshaft.
These systems use the readily available oil flow from the engine lubrication system to do the work.
Here’s how it works:
You are stopped at an intersection or just cruising along and you step on the gas. The electronic control unit (ECU) sends a signal to the variable valve timing solenoid to open its fully-integrated oil control valve.
When the oil control valve opens, there is a rapid flow of engine oil under pressure to the cam control mechanism that quickly changes cam position relative to the driving chain or belt.
The cam position can be advanced or retarded on the fly based on engine speed and throttle (gas pedal) position.
Once the engine reaches a steady state speed, the oil control valve closes and the cams will automatically return to their initial position. All of this activity will occur nearly instantly and sometimes the driver won’t perceivably feel the effects of these changes.
There is also a secondary benefit of this system. The OCV constantly circulates oil to the timing chain and associated sprockets, which increases the amount of lubricant supplied and oil flowing to cool them.
Symptoms of a Faulty Oil Control Valve
The OCV and VVT solenoid are in the same unit and can fail. The following 4 signs can warn of a failed OCV:
#1. Rough Idle.
The VVT system does not operate until higher RPMs or when under load, such as going uphill. A faulty oil control valve and/or VVT solenoid may let excess oil into the VVT system so that it has a rough idle, stalls, runs poorly, etc.
#2. Poor Acceleration.
During acceleration, the engine will be slower than usual. The power needed for going fast and/or going up hills will be lacking. Whenever you are in traffic and need to speed up quickly, or need to floor the accelerator to prevent an accident, that is an issue.
#3. Poor Fuel Economy.
I mentioned that one of the benefits of variable valve timing is fuel economy. But, this all goes away with a faulty oil control valve, as the intake and exhaust valves will open and close incorrectly. Over time, you will see your fuel usage increase.
#4. Check Engine Light.
The check engine light will come on. The onboard diagnostic system (OBD2) will store a code.
This code will let you know if the problems you are experiencing are related to the OCV and its associated VVT solenoid. You may see codes DTC P0008, DTC P0014, DTC P0017, DTC P06DD, etc.
As with ALL CEL ‘on’ event, you can drive a small distance, but it will need to be seen by a technician for repair.
What Causes the VVT Solenoid and OCV to Go Bad?
The VVT solenoid works electrically as determined by the ECU. Any problem in this circuit or a problem with the VVT solenoid can cause failure. The solenoid may have an internal electrical problem causing intermittent operation or no operation.
The OCV operates using clean engine oil. The OCV must receive clean oil, so attempting again a dirty oil valve again is pointless. If you do not do oil and filter changes according to your owner’s manual, you can build up sludges and/or varnishes (sticky deposits) in this valve.
With this type of contamination, it is also possible to slow or completely stop its function. Also, while this valve is relatively simple in construction, it can suffer an internal mechanical failure or not operate.
Many OCV installations have an inline oil screen ahead of the valve oil inlet. This screen can partially or completely block the flow of oil to the OCV. This screen can accumulate dirt or sludge, and blockage will reduce flow to the OCV, failing and potentially me an unintentional ‘delete’ of the failure condition.
Again, oh, did I mention clean oil is important? Performing periodic engine oil and filter changes may prevent this type of failure!
Can You Drive With a Faulty Oil Control Valve?
You can drive with this valve broken, but don’t drive much. You need to be at the repair shop or dealership soon.
The reason for this is that the OCV or oil screen may be partially or completely blocked. If so you will slow or stop lubrication to the cam sprockets and chains and damages to sprockets and chains will happen quickly.
It might be expensive to fix the damage.
VVT Solenoid Replacement Cost
VVT solenoid replacement may require a diagnostic fee, labor, and the cost of parts as follows:
The diagnostic fee could be $65 to $100 if charged. Parts probably will be between $50 and $250 for the average. Labor for the VVT replacement could be between $75 and $200.
All in all, you will likely pay around $210 to $550 for the entire bill.
If you see evidence of contamination and sludge in the oil control valve or filter, this may require additional work.
This would be flushing out the engine lubrication system and replacing the engine oil and oil filter. The cost of this work, plus oil and an oil filter, could be an additional cost of around $125.