Please help.

I have a 2000 F250 7.3 with everything stock except a K&N airfilter. I have been having an intermittent problem for the past couple of years that is driving me nuts. As my daily driver, my truck usually gives me no problems. I drive about 30-35 minutes at 55-65mph depending on traffic on interstates 110 and 10 through Baton Rouge, LA which is realtively flat except for a few overpasses and elevated sections. But on a number of occasions, after a normal startup and running normally for quite a while, the engine has begun to stall and lose power as if losing cylinders one by one.

I have read several posts about this problem but most seem to occur relatively soon after start up. My problem seems to occur mostly after I have been driving for at least 45 minutes or more under a bit of a load such as pulling a utilitiy trailer with my ATV and assorted other equipment.

Occasionally at the end of my commute, I will notice a loss of power as if cylinders are dropping out and when I stop at a red light, I notice a definite miss. When on a longer drive, I might lose ALL power eventually. In the past 3 weeks, I took a 3 hour trip to our hunting camp 3 different times. The first 2 times I pulled my travel trailer and cruised between 55 and 65 mph most of the trip with no problem. Last weekend, I only pulled my ATV on a utility trailer and after 35-45 mintues of driving 55-65mph, I started losing power. The power loss got progressively worse and I had to pull over and let the engine rest or idle several times in order to limp it to the next town. When I pull over, I will put the pedal to the floor and I often cannot get more than 1500-2000 rpm sustained. Grey/blue/white smoke poors from the exhaust when I put the pedal to the floor like this. When it sits for a while the symptoms get better for a while. I think it might be heat related because of this pattern of improvement after idling or total shutdown. When this happens, if I let it sit overnight, it will usually start and run normally the next day.

This time, after leaving it overnight in a parking lot 30 miles short of my destination, it started a little rough but the idle soon smoothed out and I was able drive the rest of the way to our camp. A couple of miles short of the camp, I put the pedal to the floor and when I hit about 70mph, I started losing power again and my speed soon began to drop to where I could only maintain about 55 mph. (That 65-70mph window seems to be the sweet spot for this problem if it is going to occur.) I backed off and gingerly drove to the camp and parked it. It sat overnight and the next day it started and drove like it was brand new. I drove it about 30 miles to my parents house. Again, right before my destination, I punch the pedal to the floor and this time it seemed to have all the power I wanted and never missed a beat. I am baffled. I am thinking it is some sensor or other part that is intermittently failing due to heat or a short of some kind. Any thoughts please? BTW, I just changed the oil 2 days before so that is not it. I have replaced fuel pump, CPS and ICP sensor because of other issues. I changed fuel filter about 10K miles ago, so I don't think that is it. I have changed the filter a number of times when I have this problem and it never fixes it.

Is this something electrical or computer related, or maybe the HPOP pickup tube? Don't think it is injector o-rings because I am not using any oil. Would failing injectors run normally most of the time and only do this under such specific circumstances?

Please help!

 

Welcome to FTE. How bad is the miss? Does the check engine light come on? Any codes?

Sounds like a fuel restriction. Plugged screens in the mixing chamber inside the fuel tank would be a likely suspect.

 

Welcome to FTE...You are in good hands w/Chris.Just make sure to get back with him/us so we can get ya fixed up

 

I was thinking about dropping the tank and checking the screens and fuel pickup to see if it is cracked.

I have not gotten any CELs since the ICP sensor went bad. That was throwing a number of codes when it occured. I have not checked for codes since this last episode happened. I left it at my parent's house b/c I am traveling for work this week. Plan to take my father-in-law up there this weekend when I get back to town and bring his programmer to check for codes. We will try to drive it back home and tow if necessary. Thanks for the input.

Kojock

 

BTW - i forgot to answer your question about the miss. After a really good warm up, like at the end of my commute, I notice at the redlight that my gear shift is knocking around pretty good. When I start cold, idle is smooth with normal tight vibration that any good diesel engine should have. The miss at idle is more pronounced as if maybe 1 cylinder is not firing or misfiring or something. Not like it has jumped time, but definitely not the way a PSD should idle. I have been driving this truck everyday for 7 years so I notice subtle changes in vibration, noise, etc. I forgot to mention, even after I changed fuel pump, I am still getting fuel pump noise when I turn on the key - a sort of a loud buzz/rattle at the pump below my seat. Is that a sign of pump cavitation from a down stream restriction in the screens? Sorry I forgot to mention that. Just thought about it.