What does it mean when an engine misses?

I was reading the troubleshooting part of the Haynes Guide and theres a part that says engine misses while idling or at high speed? What does it mean and how will a car behave when it is doing this?

It means a spark plug (or all of them) is/are not firing reliably. The engine will run either rough or erratically. As you can see in the manual, there are a plethora of possible causes.

Thanks. I was just curious…when an engine is running rough, can this also mean it surges erratically, or is that different?

Misfires Can Also Be Caused Improper Fuel/Air Mixture And Compression Loss.

Faulty ignition components, damaged gaskets, clogged injectors, etcetera are just a couple of the myriad of possibilities.

Here’s a link that explains the behavior and causes. Give it a click.



CSA makes a good point, I should have said it means that a cylinder or all of the cylinders are not igniting reliably. A flaky injector can also cause misfiring, as can some other fuel delivery problems.

That does not negate the list of possible ignition system possibilities, but it does recognize the fuel delivery possibilities.

Surging can be related but not necessarily. Except in the rare case where ignition timing wanders (distributor based systems had this problem sometimes when they got old, but todays cars control ignition timing much more reliably), surging is generally a fuel metering problem. Again, there are a number of possible causes including but not limited to vacuum leaks and flaky fuel pressure regulators.

Milady, would you like me to recommend some good books on automoyive fundamentals? You sound like the kind of person that is an obsessive-compulsive reader who would really benefit from good texts.