Engine code P0300?

[WItoTX]

Well, I got gas this morning (different station) and put a can of Seafoam in the tank. Yesterday I changed plugs and wires which I think were factory. They were pretty bad. The actual fix (in my mind) was replacing the MAF sensor. That durn thing will throw some of the strangest codes that are not related to itself. Ran 20 highway miles this morning and so far so good.

Good deal. Those MAF's are finicky. Glad you got it fixed and it wasn't something more serious!

[RifleBowPistol]

Miss fires are can be caused by spark plugs, plug/coil wires, coils, and or the engine running lean. If you pull the spark plugs and there is nothing obvious why they might cause a miss fire, then likely there is something else causing the problem. But if it's been a while since you put plugs in it, replace them. Then make sure you use a common replacement spark plug, such as a AC Delco, or a NGK. I would stay away from most all other plugs in that engine.

Cleaning the MAF may help, more so, if the screen looks black or dark gray. You could have a plugged fuel filter or weak fuel pump, that or a vacuum leak. Probably the reason, I most often see random miss fires, is vacuum leaks. More so on engines made in the past 20 years. Those rubber seals, that seal up the various intake gaskets and the plastic intake manifolds are only good for so long, then they will start giving you all types of problems. When I figure out a engine has a vacuum leak, I start by replacing the intake gaskets, sometimes that fixes the problem, other times it does not. When it does not, then I have to go back and replace the intake manifold. Now if I take the intake manifold off and see something obvious with it, it gets replaced right off. Most of the time, there is not an obvious problem. After replacing the intake seals, and or gaskets, if it's still leaking in the same spot, that's when you know you for sure, need another intake manifold.

[Goldeneagle]

Good deal. Those MAF's are finicky. Glad you got it fixed and it wasn't something more serious!

The CEL is on in my wifes car. It drives perfectly fine, nice and smooth both driving and idle. Code reader says she has cylinders 2,4,5 and 6 misfiring. It only has 6 cylinders. If this many were misfiring, you probably couldn't even start it much less drive it. Gonna put a MAF on it too.

[91cavgt]

The CEL is on in my wifes car. It drives perfectly fine, nice and smooth both driving and idle. Code reader says she has cylinders 2,4,5 and 6 misfiring. It only has 6 cylinders. If this many were misfiring, you probably couldn't even start it much less drive it. Gonna put a MAF on it too.

Misfire codes don’t necessarily mean the misfire is happening all the time. Sometimes, a misfire will only occur under curtain circumstances.


But you would be surprised at how an engine can run on very few cylinders! It won’t run good, but most engines can run on half of their cylinders, or less at times.

[ra61hunting]

The CEL is on in my wifes car. It drives perfectly fine, nice and smooth both driving and idle. Code reader says she has cylinders 2,4,5 and 6 misfiring. It only has 6 cylinders. If this many were misfiring, you probably couldn't even start it much less drive it. Gonna put a MAF on it too.

If both of you filled up at the same place and are having the same issues I would think bad gas would be the likely cause of your problem. Glad you got it sorted out.