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Message: [QUOTE="Heavywrecker, post: 1492563, member: 29527"] Hello, I have an 08 6.4L ford new to me....i have been battling a th. Issue since I bought the truck. I work on diesel cars and trucks for a living as well as run a towing service. My truck has been doing this thing where the frp will irrastically drop, truck will stumble and come rite back out of it. It will do it either when driving it normally out of a parking lot, down the highway or when the cruise is set. If you hold the accelerastor at a steady pace and for example at 70 mph, the frp will drop down from around say 11-12,000 psi to 2500psi, you can feel the truck loose power, it doesn't die but you can feel it stumble. Now if you give it a little gas or let out a little it will straighten rite back out and frp will return to normal levels. I tested hfcm, had 8 psi, so I replaced it with a brand new fass 165. Figured the rail pressure sensor was bad, also replaced that with an alliance part from my local international dealer in town. Truck also has a ******* tuner in it set at 250hp, tried a few settings and it does the same thing on all of them. Only thing I did notice is that there was a small amount of oil in the frp sensor connector, figured this was normal since she's under the valve cover. Other thing I noticed, after I put the frp sensor in it, I keep it in a garage overnight, I thought I had it fixed. I let it sit outside one weekend (2 days) while we had a decent amount of rain and it started to mess up the very next Monday on the way to work. Thinking maybe something got wet possibly? Other thing I noticed is that when it screws up at low speeds the wrench light in dash comes on and it's almost like it disables the throttle then if you mash is, truck starts to go slowly and blows quite a bit of black smoke in the process. Any help appreciate, you know how it is...when you do this stuff for a living, you hardly have time to work on your own stuff lol Thanks in advance! Video attached Sent from my SM-G950U using Tapatalk [/QUOTE]