If your car’s engine is hissing all the time, you probably have a vacuum leak in one of the vacuum hoses. The sound may also sound like the suction noise that your vacuum cleaner makes when you use the accessory hose. Your vehicle takes the vacuum generated in the combustion chamber and reroutes it via the vacuum hoses to power various accessories and components. One sign that you have a vacuum leak aside from the hissing sounds is malfunctioning accessories and components. Del Hatt Automotive lists the other signs of an engine vacuum leak below.
When an engine vacuum is leaking out of one of the hoses, this actually introduces excess air into the motor. Consequently, this can throw the air and fuel mixture in the combustion chamber out of whack. The mixture will become air-heavy, and you will start to notice engine problems as a result. One of these problems is that your acceleration will become unresponsive.
Engine Performance Issues
Your automobile will also suffer from engine performance issues such as sputtering and stalling. This is because the engine has become fuel-starved due to the excess air that is in it. It may feel as if your engine is going to stall while you are driving because it is constantly hiccupping. Repairing the vacuum leak usually resolves this problem.
As the vacuum flows out of the vacuum hose, you may notice that the needle on your tachometer is either registering much higher than normal RPMs or bouncing up and down. This is an indication that the excess air is flowing into the engine in spurts. Again, fixing the vacuum leak will bring your engine’s RPMs back to their normal revolutions.
Your vehicle may also idle roughly if it has a vacuum leak. It does this for the same reason that your acceleration lags and your engine performance suffers. The engine has too much air in it and it may stall during idling or idle roughly because it needs more fuel. If you park your car in a safe space while the engine is idling and pop the hood, you may be able to follow the hissing sound to the hose that is leaking.
Del Hatt Automotive in Poughkeepsie, NY, also advises that your check engine light might come on if your engine has a vacuum leak. This is because the engine control module has been advised that there is too much air in the combustion chamber.