The L started to miss the other day and we checked the spark. One of the cylinders had a poor spark so I took the cap off and found that there was a carbon trail on the outside of the cap. Aha I said thats it and put on a new cap and rotor. Still missing so I checked the wires carefully and then removed the cap again Everything looks OK but it still misses at low RPM. Any ideas? Has new wires, plugs, rotor & cap. Milage about 130K.