I have a 03 4.6 f150. Help Please. Ok so i was driving normal @ 40 mph, for about 4-5 times the rpm dropped and everything else dropped for about a second then went back to normal as if it turned off but it would turn itself back on. I really dont know what it could be. Ive also noticed that a slight vibration of the engine that is very noticible when im on drive at a light or when im on idle. Cant really tell if it vibrates when im running. Spark Plugs and Fuel Filter are almost new. Any ideas?

 

what about oil pressure gauge? Is it dropping too? If it is, sounds like crank shaft or rod bearings, but that's just a guess

 

oh sorry guys actually only the rpm needle drops and not everything. also when this happens the a/c turns off too

 

Battery

 

Did you put in a CAI and disconnect the battery recently? If thats the case, your ECU is trying to learn again. If not, what's the voltage gauge at? Might be battery

 

I just replaced the battery about a year ago or so, but i will check that out. I have a volt meter actually and when the rpm drops the voltage stays the same