During the last couple of weeks my truck has started to randomly miss at part throttle. It will start to miss, or buck, usually after I have been on cruise control for a while. I cancel the cruise, and then throttle up. Usually it clears up and then runs normal, although sometimes it will continue to miss for a bit. Once cleared out, I can run WFO with no problem, in fact it doesn't seem to miss if I am running the bag off it, just when I have been running at light throttle for a while. It acts like there is an air bubble that gets into the system, and then it works it's way out. There are no codes when I check, except for a P0514 that has been there for a while. That is a battery sensor thing, time for new batteries I think. I have changed the fuel filter with a new Baldwin 7977 and no change. I thought maybe it was bad fuel, so I made up 90 gallons of double strength Power Service, and ran that through. No change. I get fuel from the busiest place in town, and have gone through a couple of hundred gallons since it started, from a few different truck stops, so I don't think it is fuel. The truck starts great in the morning, even not plugged in at -8c the other day, and no smoke. The oil level is rock solid, I check every morning. The miss has gradually been getting worse. It used to just do it once in a while, now it is starting to do it almost every day at least once. Also it died today on the way home. I stopped at a stop sign, and the idle started to lope between 400 and 1000 rpm. Then when I tried to give it some gas it died and would not restart right away. I shut off the key, then turned it back on and made sure the lift pump was running, then it fired right up like normal. Not sure what to make of that. A buddy thinks it is the lift pump going, but I don't think so. Usually they either work or don't work. I have never heard of one that cuts in and out, and I can run WFO with no problems. I have the in tank lift pump. Maybe it is an injector that is not firing sometimes? It is not a regular miss, just once every second or two, and sometimes a couple misses close together, hard to explain. If anybody has any ideas, please post them up so I can try and get my truck running properly again. Thanks.

 

BTW, I have a 90 gallon slip tank with a 10 micron filter/ water separator. I always fill the slip tank and top off the main tank from the slip tank every night. I try to never go below half tank, and the miss has occurred whether the tank was full or half full. If it was sucking air, you would think it would do it at the lower levels, not when right full.

 

i think you have an injector that is sticky. that bad the dealer can get a reading on witch one it is

 

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I have heard of this before. I think you have a bad solenoid on one of the injectors that won't fire sometimes. My truck has done something similar, it will have a slight miss at idle though. It's done it twice but not in over 6 months. I would take mine out and run the snoot out of it, problem solved.

 

That is kinda what I was thinking, a sticky solenoid, but my truck idles perfect. All the threads I searched about missing, were about missing at idle. Also like your truck, if I bag on it, it gets better for a while. I am thinking about pulling the injectors and sending them in to be rebuilt. I don't know much about the history of this truck, so I might as well get them all checked out. Anybody know if there is a good place in Alberta, or even Canada to send injectors?

 

I don't think it the solenoid is sticky, it is just not firing the coil so the injector no worky right....LOL It may be weak and when the injector gets carboned up it acts up. Mine has only done it twice and the last time has been a while.

 

Makes sense. Thanks. Wonder if maybe it could be a loose or poor connection at one of the injectors? I wiggled all the connectors at the valve cover with no difference. Later on this winter I am planning on pulling the valve cover and maybe the injectors.

 

Yeap, I need to do the same and send my injectors to Don M. at F1.

 

It turns out it was the connector for the rail pressure sensor. The miss/buck eventually got bad enough to give me a code, high rail pressure. After a quick search here, i came up with the cure. I cleaned the rail pressure sensor connector and re-connected it and my truck is running perfect again.

Thanks to the DTR forum.

 

sorry made a new thread