Run cold engine Test
If you run a cold engine test then it will give you a good idea whether your valve is faulty or not. In the case you are having a car then once your car is outside for a long time then after checking the top position of the cylinder inside the valve cover you will come to know that there is some residue loyal present on it. This shows that you have a bad valve stem seal.
Also when the engine is on then the residue layer of the oil can be seen on the top position of the cylinder. This results in a bluish smoke coming from the end of the pipe.
Idling is another sign of a bad valve and it can be changed when your car begins to idle for a long period. When idling happens you can see a great amount of vacuum generated at the intake manifold because the throttle valve will always be closed. Also, the high volume attracts the oil in the heads while causing it to concentrate on the valve stems. Once you accelerate the car the eroding seal allows oil to sleep on while going through the valve guide. This will exhaust the oil completely. However, the burnt exhaust generates blue-white smoke that will come from the tailpipe once the car stops the acceleration.
It is another sign that your valve is running poorly. The excessive presence of exhaust smoke especially with the blue-white color may last long after starting the car or while accelerating.
However, on the other hand, the smoke may disappear after a while which can again mislead the function. Bad valves usually signal in the excessive oil burning issue.
Loss of engine power
The shortage of acceleration power when you engage the Gas pedal also produces faulty piston rings as well as check valve seals. In this issue, a compression test will help you to identify the problem if it is occurring due to the valve seal or the piston ring. Traditionally you must remove the EFI fuse and crank the engine. Then after you must use the compression gauge to check the final result.
Excessive oil consumption
Oil helps components to get lubricated in the engine that will help in the smooth functioning of the engine and hence excessive oil consumption can be a serious problem that shows that the friction is not working properly.
If the oil consumption is high then it is due to the oil leakage or the oil-burning excessively leading to a quick decrease in oil as compared to the normal. To identify whether the oil consumption is because of the leakage or because of the valve, then you must rectify if there is a leakage in the engine.
With these signs, you can check and know if your valve is bad.