Misfiring Cylinder?

When I start it, it idles roughly for about 30 seconds, the check engine light flashes, then it goes away and drives fine. According to the mechanic who cleared the check engine light the first time it flashed, cylinder #4 is misfiring. I am handy, is this an easy fix?

Probably not an easy fix, since you don’t really know WHAT needs replacing or cleaning… I’d let a good independent mechanic fix it properly.

It could be very easy, it could be tough.

How many miles? How long since you changed the spark plugs?

You should be able to rent a spark tester from a parts store for free. I would start there and check to see if you are actually getting juice to the plug.

Most likely, you have

  1. Bad spark plug (EASY)
  2. Bad wire (EASY)
  3. Bad ignition coil (EASY)
  4. Bad fuel injector (harder, but a DIY job with a manual IF you go slow and take your time, and walk away if you start to get frustrated).

BTW, I agree with Docnick that the tough part can be finding which part needs replacement. But a simple spark tester might find the problem very quickly and painlessly for you. If you find a store that isn’t busy and with decent help, they’ll even come out and help you use the tool to diagnose the problem.

This could be very bad–the same thing happened on my '98 civic and the misfire was due to low cylinder compression. Do (or have a mechanic do) a compression test to rule out a serious engine mechanical problem.
Also have an auto parts store pull the codes from the computer (most do it for free).
Spark problem is easy, fuel injector difficult, anything else is for a professional.
If it is not spark or fuel injector problem, could very well be a valve.

You might want to check cylinder #4 for a leaking injector. If there’s a leaking injector at cylinder #4, the gas will leak into that cylinder as the vehicle sits. Then when the engine is started, this excess gas plus the gas the injector is introducing will cause that cylinder to misfire due to a rich mixture. Once the engine runs long enough the excess gas is cleared from that cylinder and the engine runs smoothly.

To check for a leaking injector, let the engine sit idle for time it takes for the problem to occur. Remove the spark plug for #4 cylinder. Stick a rubber hose in the spark plug hole and then sniff the end of the hose for a gas odor. If there’s a gas odor that injector is leaking.


I chased an error like this for months- new plugs, new ignition coil, compression test, I tried it all. When I ran out of options I had the dealer do a valve adjustment and it fixed everything.

Just one more idea to throw on the pile.