engine revving up and back down
 

2005 6.0 powerstroke 90000 miles all stock new ficm Just cleaned egr valve. will be driving along and engine will rev up and then back to idle kinda surging. Shop said code was turbo underboost and wanted to clean it saying it was dirty. But same time experiencing no power at all when taking off. Shut off truck and restart then loss of of power symptom goes away says could be accelerator pedal sensor going out but no codes for it. Could both be related, if anybody has any idea or shared same problems i would appreciate it

mine would idle like crap then i'd have power just kick in like crazy before. Does it start up and idle kind of crappy then all of a sudden feel a major power band kick in randomly? Mine would do that. Or run like crap for a couple minutes then i'd be sitting at a light waiting for it to turn green and it would kick up power then and i'd have to hit the brake harder to not rearend the car in front of me. If it's something like that it could be your ICP sensor getting messed up. That's what happened to mine. Had to replace it. Should have a CEL for it on though, I'd imagine.

Any access to a scanner of some sort? Have you tried reading codes on it yet? It doesn't need to have the check engine light on to have codes either...

Welcome to DB!

the only code is turbo underboost p0299 no cel light comes on Im at a loss

This is odd...

How long has it been since oil was changed? What oil is used? What oil filter? What about fuel filters? How long and what kind?

Any mods on the truck? How many miles? Any more info about the truck you can give will help.

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oil changed 2 weeks ago from dealer we bought lifetime oil changes with pickup. 15w 40 not sure of brand, fuel filters r 3 months old filters are napa brand no mods and 90000 miles as stated in original post wife drives truck the most and i know she doesn't drive it hard. and especially now that it loses power. she says it acts like there is no gas pedal upon take off it justs idles but if you shut truck off and restart it it works fine again for a while. The guy who read the codes for us said the turbo was dirty, but also said the other problem could be acclerator pedal sensor. I just dont want to change stuff out and that not be the problem. one would think if the turbo stuck you could run some additive through it and blow it out maybe run it hard also

The pedals sensors do go bad, but it's quite rare on these trucks.

When you say additive, what do you mean? How is an additive going to clean the turbo? You need to pull it out and physically clean it, but I'm not sure that's the issue either.

First things first, I'd lose the Napa oil filters, go with motorcraft ONLY. Any filter that uses it's own cap is dangerous on these. There's a button that is pressed in when you put the oil filter in to allow oil in to the housing. Some of these other brand filters don't press that button very securely and can starve the motor of oil. This could cause running issues since the injectors are fired off of high pressure oil as well.

Turbo cleaning procedure here: DTS Articles - Turbocharger Reconditioning

Running it hard helps keep it clean as well. Idle time and driving like a putz are the two worst enemies for these turbos. :c:

the oil filters are motorcraft since dealer changes oil, the fuel filters are from napa. The wierd thing is it seems to happen during daylight when air is less dense. in early mornings the problems dont occur. and the only code on it is turbo underboost. Im going to check conditon of hose to and from turbo and air intake. air filter is fairly new also. It is puzzling since had no prolblems with truck till past 2 months. Thanks for all the help

The first thing that came to mind is an injector issue. No fuel will cause an underboost, but i dont know what the computer monitors specifically to determine an underboost. Hell, what do i know...


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It must monitor vane position and EPB sensor input I would think... Map sensor too?

Actually...

Check the map line, it's a vacuum line that plugs in to the top of the intake manifold on the passenger side. Make sure it's plugged on the nipple all the way.