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Discussion Starter #1
In the past three months I have had episodes where I go to accelerate and the truck falls on its face(slowly accelerates then jumps RPM's and takes off) I thought once before it was a fuel problem and changed my filter. That seemed to take care of the issue. A few weeks later I came across the same thing again, So I changed the fuel filter again. It has happened 2 times this week and I can't figure it out. The check engine light hasn't come on, I do have a stored code for low fuel rail pressure(I think that is from having the downloader-Bully Dog Power Pup) Is it a possible injection pump issue or computer??? Any info will be greatly appreciated, Thanks Guys

Chris Zimmerman
 

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Discussion Starter #2
Sorry Guys the above truck is a 2003 Sierra 2500HD 2WD Duramax w/ 109,000 miles on it...

Chris Zimmerman
 

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have you checked your thottle position sensor (the one on the pedal). Sounds like there is a dead spot in it.
 

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Discussion Starter #4
What should I look for when I check it???

Thanks,
Chris Zimmerman
 

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Discussion Starter #5
Also if that were going bad wouldn't a code come up???

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Chris Zimmerman
 

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There should be a way to use a multimeter to shoot it as it is just a potienometer. If you know someone with a predator for your year truck you can check your switch that way. I have read on other forums that people have had no throttle response and had to idle to park somewhere. I don't think you would get a code unless it was completely open. One other thing that you can do is to see if the thottle move freely with your hand...if it is binding on say the carpet, then that could cause what you are seeing.
 

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Discussion Starter #7
I went to my buddies shop and used his Snap-On scanner and took the truck for a test drive to check the throttle position sensor, everything checked out normal. I guess with it only happening every so often it will be hard to check that way. It never happened. Nothing is binding under the pedal. I am gonna check on his Shop Key to see what they as far as checking with the multimeter. At idle it sometimes goes up and down +50/-50 RPM's, I am sure the throttle position sensor could cause that aswell. Is the sensor by itself or is it the whole pedal assembly? I am assuming its a dealer only part.

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Chris Zimmerman
 

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I think it is the whole pedal assembly. According to alldatadiy, it says to check it with a scan tool without starting the engine...just have the key in the run position. That way you can use your hand and not your foot. As far as the rpm going up and down....that is probably the fuel pressure regulator valve doing that.....it's called a loping idle. some trucks do it so bad that you can hear it. +- 50 isn't that bad I don't think....I will have to check mine out now.
 

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Discussion Starter #9
I am not a member at alldatadiy.com so I will have to look into checking it without the truck running, see what I am going to be looking for atleast. Where is the fuel pressure regulator on the engine?

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Chris Zimmerman
 

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Discussion Starter #10
I am assuming that the correct name is the APP(Accelerator Pedal Position Sensor)???

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Chris Zimmerman
 

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Yes, APP is the right term for the sensor I am talking about. I checked my truck last night and it only varied about 15 rpms at idle. the FPRV is on the engine. As far as what you are feeling with the truck just acting sluggish and then taking off. Have you been changing the power levels much with the bully dog? My predator kinda does the same thing.....if you give it a little throttle, sometimes it doesn't take off fast, then it decide to pull hard. Also, when this is happening, is the truck at operating temp or is it cold? Also, I would try and clean the mass air flow sensor as it might have some dirt/oil on it from the k&n. I would just use electrical contact cleaner or rubbing alcohol and a q-tip...be very gentle with the resistors on the MAF sensor. Also, your wastegate could be going out.(blowing open) You don't have a boost guage do you?
 

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Discussion Starter #12
Yes I do have a boost gauge and there seems to be no problem with the boost, I will clean the MAF today and see if it helps any. I am wondering if I hoop the scanner up to the truck to check the APP sensor if it is gonna show if its going bad or has a dead spot(Since the problem ins't a contstant thing) I am sure it is something stupid, one minute it runs like a top then one minute it has no acceleration and then takes off like a bat out of hell....

Thanks Again,
Chris Zimmerman
 

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Discussion Starter #13
I don't play with the setting on the Power Pup, It has been on the towing setting(50HP) since I first installed it...

Chris Zimmerman
 

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bringing this back from the dead...i got the same issue...what was the fix?
 

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having similar issue. I noticed if I unplug my maf it eliminates the accel problem but throws codes. been chasing ghosts on my 01 for months.
 

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having similar issue. I noticed if I unplug my maf it eliminates the accel problem but throws codes. been chasing ghosts on my 01 for months.
Same thing here! Anyone find a resolution? Mine is nearly the same exact symptom description. Been driving me nuts!
 

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Bump

<Bump>
 

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Same problem

Hey guys, my LLY has recently been doing the same sluggish acceleration as of recent. Today the truck fell on its face, so i pinned it and then three codes appeared. They were P0401 EGR insufficient flow, P0404 Exhaust Gas Recirculation Open, and P0101 Mass Air Flow Sensor Circuit Range/Performance. Any and all adviced is appreciated.
 
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