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Q: After a tune up I got a misfire in cylinder 3.

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Got my car scanned bc of a check engine light and found out I have a misfire in cylinder 3. Car starts and runs fine until 3000 rpm then it starts to pull back and forth and try to hisses.

My car has 85000 miles.
My car has an automatic transmission.

The hissing sound may be an indication of a vacuum leak, which may be causing the hesitation and misfire. High idle speeds or in some cases rough idle, stalling and hissing sounds are common signs of a vacuum leak. When a vacuum leak is present in an engine, this causes an excessive imbalance in the air/fuel ratio which creates a loss of power and causes the motor to run at a much higher RPM as a result of the increased oxygen present in the fuel charge being injected into the motor. The pulling once you reach 3,000 RPM is likely a result of too much air present (as a result of the vacuum leak) in the fuel/air charge, essentially causing the motor to starve for fuel at higher RPM’s. As you increase the throttle, the need for additional fuel and air is needed, however the vacuum leak introduces too much air creating an imbalance. I would suggest having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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