Hello: My husband's truck has been acting up for almost a year and it is getting progressively worse. There are no engine light displayed or diagnostic codes revealed.The one time I was riding in it at the time, approx speed 50-60 mph, when it missed, it reminded me of the rumbling sound the diesel engine makes for start up. My husband says it also misses when it is idleing in park. So far we have replaced the following: Injector fuel pump, lift fuel pump, crankshaft sensor and cam sensor. Our dealer is stumped. At the end of the day, there does not appear to be any specific range of 'rpm's' that this problem occurs. It's a hit and miss basis. The truck has 135K miles on it and we are the original owners and do regular maintenace, oil changes, fuel filters, etc.