Power loss on highway...HELP!!!

So I am driving down the interstate going 75ish (the speed limit) and my truck feels a little sluggish. Just figure it's the new 275/70/17 KO2s, flatbed, and the 12mph cross wind killing me. Well after about an hour of driving the truck starts to loose all engine power and I push the pedal harder with no response. Then all of the of a sudden it picks back up acting like nothing is wrong. What in the world could it be? According to my ultragauge I have pending p0171 and p0174 codes but they never got set off. I also just unhooked my catch can before coming into my destination thinking maybe it is full and the pcv is getting clogged. Truck is a 07 DCLB with a Volant air intake and has 149xxx on the odometer.

 

Could be your fuel filter getting clogged. Check your fuel rail pressure. Maybe water in the fuel?

 

I stopped at an auto parts store and got some seafoam to help if it would be water in fuel. I did stop at a gas station I normally don't go to last night but only put in 5 gallons so that's a maybe. I'll have to check my rail pressure later tonight when I get home and have the comforts of a garage and not the side of the highway if i make it...

 

Just a thought... But this probably should throw a code - Too much vacuum in the tank ? / bad cap?

Also note the fuel level in the tank when it happens. IF it happen when it's fairly low only, there might be something in the tank (i.e plastic baggie) that gets sucked on the fuel filter and then releases and floats around some more. This happened to a friend of mine. He figured that someone stuffed it in his gas tank ....

 

Too much vacuum in the tank is a total possibility! Sometimes my truck doesn't want to take gas but I'm unsure as to how to fix it.

 

OK, others here have more experience in this area than I have, so they can chime in ....

First I'd throw in a bottle of dry gas if you have not. 2nd check / replace the gas cap. 3nd (if Equipped ) I'd check the tank throat to be sure, if there is an anti siphon flap / door/device that it is working correctly and not blocked/sticking/missing, etc. 3rd I'd check the hose/overflow hose at the throat of the tank - make sure the hose is not cut, attached securely, not kinked etc. That hose should attach to the emission system - sometimes a canister. Check the entire hose length an if it attaches to a canister - check it for cracks/leaks/plugged vent hose, etc. On older vehicles these sometimes had a filter in the canister check that as well and ensure the canister is not loaded with old overfill gas.

Some of the info I listed is dated - but quick to check.....

 

Maybe there is a miniature black hole in the Evap canister? Unlikely. I bet it isn't getting enough fuel. The sucky part is you might as well change the fuel pump if you change the filter, as it's one of those in tank jobbies. Urd makes an external filter kit with a new pump and internal filter. That's what I have on my truck.

http://urdusa.com/store/p1260518592...uel-Pump/Filter-Upgrade-Kit/product_info.html

 

It ran Iike nothing ever happened on the way home so I am wondering if my catch can was full enough that the pcv was taking in oil and it was causing it to be sluggish. I'm going to play with my hoses on my tank since they are modified due to the flat bed and try to rid myself of the vacuum problem because it happens every so often but then corrects itself. Thanks guys for all your help.

 

Old Vehicle Non EPA Tanks used to vent to the atmosphere.
Blocking the vent on these and small engines causes a vacuum lock and prevent pressure differential that is required for the atmosphere pressure to push /feed fuel to the pump input.

When the EPA arrived it wanted the gas vents changed so a partial vacuum was made with a sealed gas cap on the tank. Slight Vacuum from the engine is used to draw the vapors from the tank through the evap canister and then into the engine intake. If the system is messed up the vacuum can increase and prevent the fuel pump from pumping.

It's no so much a poorly sealed cap but one that is not working correctly.

 

Well my mass air flow sensor was coated on one side with almost like oil which is odd because I use a dry filter but I guess with dirt and moisture it can cause a grind to build up. On a test run to see if that's the culprit

 

Check vacuum hose that goes to fuel pressure regulator make sure it's hooked up. It's the skinny hose on your air intake.

 

If you are pulling those codes then start with them.

 

I was lead to believe that the vent to the air was still In the cap - but at a less than ambient temp. If that should block the vacuum could increase.?

 

Ours don't work that way. The fuel pump is in the tank, and there is a return line for unused fuel as well. Then there is a bunch of Evap stuff hooked up. There is an evap pump that applies a vacuum to the tank, siphoning fumes off and sending them back to the intake. If you leave the gas cap off, the pump can't apply vacuum and it throws a code. Truck runs fine though, it's just an emissions thing. The gas cap is normally sealed.

 

Well after cleaning the MAF it still did it if I jumped on it on the interstate but otherwise it drove fine.

 

Check your fuel rail pressure under full power. When did you last replace your spark plugs?

 

Nope I made sure everything was all buttoned up right. Spark plugs were done roughly 25,000 ago. I'll probably do those today as well

 

Well just pulled a plug and the gap looks too big. I can just about squeeze a dime in which is a .053 so that's way out of spec. Looks like this might be the culprit. I was told they were gapped right and couldn't find a gapper so I just put them in. Stupid me

 

Well after changing the plugs, taking my catch can off, cleaning my MAF and a bottle of seafoam in the tank I'm down to just a p0171 code and not a p0171 and p0174 code. Not sure what it could be now.

 

You guys are lucky, I haven't driven my truck in 2 weeks