Expert: HT - 5/17/2007

Question
Hello, Helping a friend with a '03 Hyundai Tiburon, that runs rough in the morning, or when it has been sitting for awhile. I used my obdII reader, and the car is throwing 300, 301, and a 302 problem codes. New plugs, and wires, but still seeing these codes. Maybe a crank sensor? Any help would be great. Thanks in advance

Answer
P0300, P0301, and P0302 are all misfire codes (cylinders #1 and #2, and a multiple/random misfire).  The only time I've heard of this being related to a crank sensor is if the sensor were loose.  Furthermore, a crank sensor issue should affect all cylinders equally.  So I'd expect you'd have the P0300 only, or all the codes you have plus P0303 and P0304 (and P0305 and P0306 if a V6).

You should continue checking your secondary ignition system.  Presuming the wires and plugs made no difference in the codes or condition, check the coil.  You'll want to do your checking when the problem is occurring.  Perhaps even mist the wires and coil with water to see if you can see a spark jumping.  If you do indeed see a spark jumping, that is the location of your problem.

Another strategy you can use is to take the #1 and #2 plug wires (if accessible) off the plugs and just set them back in place without clipping back onto the plugs.  Then, start the car, and gradually pull the wire(s) off the plug(s).  The spark should come out of the end of the wire onto the plug.  If it comes out of the coil or the side of the wire, then the problem is in the location of the spark.

If you're unable to find a secondary ignition problem, then you should begin investigating whether you have a fuel delivery or internal engine problem causing the misfire.  Most engine issues will show up with a compression test.  If you indeed are only misfiring on cylinders 1 and 2, you can swap those injectors with the others to see if the misfire follows the injectors.