looking for some help on where to look for a problem. Truck is not running right. I thought the problem was tied to my quad box, but it only amplifies it. When under light throttle such as going up a slight grade truck cuts out and feels like it is bucking. Another thing I noticed that it is doing when driving 45 or so and steping on it fairly hard to get back up to highway speed, boost will run to 32 lbs then quickly cut back to 25-28 lbs then back up to 32 then drop down once truck shifts. I passed a vehicle on the highway today and when I got around them I looked down and the boost bounced back and forth 4-5 times then dropped back down once it shifted into od. Rail pressure relief valve?, could this also be bleeding off at low rpm and causing the bucking? Truck kicked a code a couple of days ago 0069 map -barometric pressure coeffiecency(spelling?) I cleared the code and it kicked back on later in the day. I checked all my connections to quad box, cleared code and it has not came back on the last three days. Quad box is totally unhooked at this time so I can rule it out as the problem. Fuel filter has been changed recently, Ive changed it twice since it started the bucking. I also run gray powerserve with every tank as well as a bottle of fuel injector cleaner every 2-3000 miles. I have been driving 120 mile trip 2-3 times a week the last month so I shouldnt be carboned up from short in town drives.

Sorry this is so long but I wanted to get as much info as possible. Any help with where to look would be great. Quad if you read this sorry I placed the blame on your box, but I would still like to get it updated to the newest program to help driveability and will contact you shortly about that.

thanks

 

My truck would do exactly like you say but only under moderate to heavy throttle. I fixed the problem with a FASS pump. I don't see a pump listed in your sig so I assume you are still running the stock filter mouted lift pump. Do you ahve a fuel pressure gauge. If you do what are the pressures you see when this happens? With any pressure box or module it just worsened the problem.

 

I had a in the tank pump put on the truck under warranty due to low fuel flow. I do not have a fuel pressure gauge, so I could'nt tell you what the pressure is running at.

 

Read this. Maybe you'll get lucky.

https://www.dieseltruckresource.com/...ad.php?t=81936