My Car Engine Has a Miss Fire In a Cylinder

Reader Question

I’ve changed all the spark plugs, coil pack in cylinder 3, new injector in cylinder 3 and i still have a cylinder 3 miss fire, what else can I do?

Please help!!!

Hi there,

Well, I would check compression on all cylinders, you could have a mechanical missfire like from a valve problem.

If compression is low on that cylinder, you will need to remove the valve cover first and make sure valve springs and push rods etc. are all ok. If ok, then the next step is to remove the cylinder head and send it to a machine shop for a valve job.

Double check for a vacuum leak under the hood first, I have been fooled before

Austin Davis

Reader Follow Up

I cleaned the throttle plate, all around the engine and Cylinders and I just checked for vacuum leak and a PCV hose had a long crack in it, I will replace the hose, could this be the problem? If not , I will check compression,

I really appreciate your help. I did do a quote with progressive, awaiting to speak to a representative.


Hello again Reggie,

The hose COULD be the issue causing a vacuum leak like I suspected, would be worth repairing first before you spend more time and money. You might want to check for vacuum leaks around the intake as well, with a can of WD40 or propane tank with a rubber hose attached to help you locate the leak. Keep all flammables away from spark plug wires or anything that produces a spark 🙂

Austin Davis

Posted in: Running Problems

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