DJHester

Thanks

My Truck (08 F350 SRW 4X4 Auto Crew Cab long bed)is intermittently running bad. I have 15000 miles on it and have had it to the dealer twice but they cannot duplicate the problem. I cannot make it have the problem. The truck may go 25 miles or a thousand mile between the occurrences. Here are the symptoms. 1. The Fuel economy (Empty is 12.5 MPG Highway and 11-11.5 MPG in town) (towing Small trailer with two 4 wheelers (about 2000 lbs) highway 9.9 MPG). Hand calculated. 2. Sometimes puts out enough white smoke out of the tailpipe that you cannot see the vehicles behind you. (it did this one time at Idle in park). It usually does this after a cruise speed of 40-50 mph then a moderate increase of the throttle to get to 60-70mph. The smoke also occurs if I cruise at about 40 mph for about a mile then stop. After taking off at a moderate excel it starts smoking. When it smokes I always get an engine miss (runs rough) but never a check engine light. The smoke and miss last about 45 seconds then it starts running fine again. 3. I drive about 100 -175 miles a day and it seems to go into regeneration about twice a day (I can tell because the exhaust pings and crackles from the increased temps and the idle is high). 4. The truck is sluggish on moderate excel from a stop and may surge till I get to highway speeds. 5. This may not be associated with the bad running but may give more info. I do not know if this is normal or not because I have not driven another 6.4L. There is a tapping sound that starts off Idle on a light to moderate excel. This tapping or knocking is very fast and goes away at about 20mph or under heavy throttle. The other knocking noise is under light loads at speeds of 20-45 mph this sounds almost like a piston slap and about the right tempo, but the knock is a little higher pitch. Almost between a piston knock and a lifter tap but is sounds too fast for a lifter. The interesting thing is I live in Houston and I took a trip to Colorado. I drove around Colorado for about 1500 miles and the problem never occurred. The truck got about 13-13.5 mpg which I have never got in Houston. I don't know if it was the altitude or the cooler weather. Thanks too all who help