Hyundai Repair: 2003 Yyaundi Accent, fuel injector cleaner, bridge the gap

Question
Need urgent help - Reading PO302 - 4th cylinder problems - engine light flashing - erractic idling - have changed spark plugs, have used good fuel injector cleaner - still having problems?  How do you know if the pvc value is clogged or needs replaced?  Any other suggestions that you have that could be the problem...

Answer
A PCV valve is designed to allow crankcase vapors to be sucked into the intake but not allow any flow in the opposite direction.  So, if you wish to test it, the easiest way to do so is to blow through both ends.  You should be able to blow through the end attached to the valve cover but not through the end attached to the hose going to the intake manifold.  You may wish to have a couple small pieces of hose you can attach to the valve to do this test.

That being said, a clogged PCV valve will not cause a misfire on only one cylinder.

The most common causes of misfires are with the secondary ignition system (spark plugs, coil, plug wires).  Since you've replaced the spark plugs and still have a misfire, we'll presume the spark plugs are not the cause of the problem.

I typically use the following to test the plug wires and coil.  If you have the 1.6L engine, there is enough insulation on the wires that it shouldn't be a problem.  If you have the 1.5L engine, you may wish to wear electrically insulating gloves to prevent shocks.

With the engine off, remove each wire from its spark plug and gently put it back on so that it doesn't snap into place.  Then, start the engine.  Now, gradually pull the wire off the plug.  The spark should continue to fire out the end of the wire boot to the spark plug (or whatever else is closest) until you get so far away that the spark cannot bridge the gap.  If spark is emanating elsewhere from the wire or from the coil, the part from which the spark is emanating is defective.  In your specific case, I'd recommend starting with the #2 wire since we already konw that is the cylinder that is misfiring.

If you find nothing abnormal in the spark test, you should check the injectors.  Since you have only one cylinder misfiring, simply swap the fuel injector on that cylinder with the fuel injector on another cylinder.  If the misfire moves to the other cylinder, you know it's the injector.  If it stays on #2, you know it isn't the injector.  You can perform a similar test to with the spark plugs if you want to doublecheck that the #2 plug isn't the culprit.