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Q: Found misfire on all cylinders by code reader. I checked vacuum and it was low at 14 hg. I checked compression 160 to 180 except no. 3 cylinder 180 to 270.

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Any idea of what is going on

My car has 150000 miles.
My car has an automatic transmission.

Hi and thanks for contacting Your Mechanic. When it comes to a misfire, first check for spark and make sure that the spark plugs are functioning correctly. Then check the fuel injectors and make sure that they are not plugged or dripping. Check the engine for vacuum leaks on the engine. Check the vacuum hoses on the intake and the brake booster. For 5 cylinders to have a lower compression and only 1 cylinder with a higher compression, there could be an issue with the valves not sealing. There could be excessive carbon deposits on the valve train or the valve springs could be weak causing the valves not to seat properly. If you need further assistance with your misfire detected, then seek out a professional, such as one from Your Mechanic, to help you.

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