The car got CK home and he came by my house so we could check it out. He has a 1996 Subaru wagon so that means that my code reader would work. Since 1996, all cars use a OBD2 code reader interface. (I think OBD means On-Board-Diagnostics.) Mine looks like this and it cost about $70 at my local cars parts store.
I have used it several times and it has more than payed for itself. The hardest part of using this is finding the plug location on the car. So far, it has always been inside the car and somewhere under the dash. Sometimes it is easy to find, sometime it is under a cover, sometimes it is out in the open and sometimes I have to fish around while upside down under the dash. The plug is standard but the plug location is not.
CK's code number translated to misfire on spark plug number one, so he bought some new plugs at Walmert for about $10. By the way, changing plugs on a 96 Subaru is not easy due to the small space between the cylinder heads and the cars frame. On removal, the old plugs had a way out of spec gap, more than .06" instead of the specification of .044". Plug gaps increase over time as the metal wears off and if has a negative effect on spark quality. Here are the old plugs.
They all look about the same, which is good. If one was fouled or very different in appearance, it would suggest the existance of some other issue.
Using the same code reader, we cleared the codes from the cars diagonistic system.
CK took the car on the spring break camping trip the next day and he later reported that the gas milage improved from about 21 to about 25 mpg and that the check engine light did not come back on. The improved milage means that even at $2.25 a gallon, he saved $10 on fuel costs in about 500 miles of driving. Wow.
