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P0299 and VGT not cycling after stc and turbo cleaning.

11K views 60 replies 4 participants last post by  nighthawk285 
#1 ·
i've got an 05 f250 with 155,000 miles. Within the last 20,000 miles its had a reman turbo, blue spring, new icp, new map, new ebp, 2 new injectors, oil cooler, egr cooler, egr, dummy plugs and stand pipes.

The truck was having a slightly long crank period so i decided to do the stc fitting. Everything went fine with it. At the same time i slow took the turbo apart and cleaned the vanes and unison ring. I put everything back together and the truck started with no problems. Its been about 500 miles since i did this and i keep getting a P0299 code. When driving the truck will lose power slightly for a short period of time (will happen on the highway with cruise on going 65mph). Then i get the p0299 code. Other than that the truck runs great. This happens completely randomly. It may do it on a 20mile drive or it may not. It doesn't always do it. I boost up to 26psi and it feels like i've got alot of power. I've cleaned the EGR and the EBP sensor and tube.

The things i'm seeing are VGT duty cycle at idle stays rock solid at 85%, if i hit the gas it will go down but then slowly make its way back up. The VGT does NOT cycle. My icp at idle goes between 578 and 585. Everything else seems perfectly normal to me. I'm using a cts2 to monitor. at 65mph boost is 4-8psi and egts are normal.

I'm thinking this is a VGT issue because i'm not sure why its not cycling. What could be causing this.
 
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#2 ·
The P0299 code is the underboost code, which is relating right back to your VGT% issue. The computer is trying to command the VGT to open (as you push down on the gas), but it's not seeing your boost increase, so it re-closes the vanes closed to try and help build boost. 4-8psi at cruise is normal, as is about 26psi (depending on elevation) for max boost so at this point I'd rule out a boost leak....have you checked for exhaust leaks? Specifically, the bellows and the connection from the y-pipe to the turbo. These are both common leak points especially after doing a turbo R&R. What are your EBP values?

If those check out ok with no leaks, it's time to take the turbo back out and make sure nothing happened during reassembly that jammed the vanes/ring and that the swing arm is moving freely (should move with some resistance but not be excessively hard to move).
 
#3 ·
I'm going to go and pick up a scangauge 2 so i can properly monitor my EBP. my cts2 doesn't monitor it properly.

When i took the turbo out i specifically removed the y-pipe an checked it for cracking. i did use exhaust wrap and wrapped the y-pipe but i left both bellows unwrapped as a precaution. When i put everything back together i did hunt for exhaust leaks because i was paranoid that i was going to have one and i didn't hear anything.

where is the swing arm located in the turbo?
 
#6 ·
it reads 0 KOEO. and i've heard that multiple people have the problem. It does move when driving but it just doesn't seem right. like when i look at my datalog at 66mph 4psi boost it reads 7.6

do you think that when i cleaned the turbo i may have reassembled wrong an caused some of the vanes to stick? would a really small exhaust leak cause the vgt to read 85% at idle but act normally most of the time while driving.
 
#7 ·
Lol uh, 0 psi KOEO and a 4psi/7psi split for boost to EBP is perfectly normal. What are you expecting to see?

Yes I think something is jammed or stuck because you're getting the underboost code ....85% VGT at idle is also normal but it should drop down to 20-15% as you go to WOT....not stay at 85 like you said
 
#8 ·
i was just seeing the scangauge 2 reading EBP at like 14.5 KOEO. So maybe they just read the numbers differently.

I'm sorry. I wasen't 100% clear. It reads 85% at idle. When i drive it does change. at WOT VGT reads 36% an it drops to 15% for a split second when i let off the gas and then immediatly climbs back up. normal cruising at 65mph it reads low 50's%
 
#9 ·
it reads 85% at idle and doesn't move at idle referring to the fact that i'm not seeing it cycle at idle.
 
#10 ·
That's because yes a scan gauge reads the value differently depending on how the users enter the formula. If they just enter it as EBP then yes, it'll read atmospheric pressure at KOEO and gives you the full pressure reading. The CTS2 gives you EBP-BARO to give you the reading of back pressure from the engine, without atmospheric pressure making noise in your data.

Ok, now we're getting somewhere....those commanded VGT values are also right where they should be so the only problem we're trying to solve would be the underboost code that is usually derived from something sticking in the turbo
 
#13 ·
I dont remember if it did before. I really didnt pay any attention to it. Its a completely stock tune. No tuner on the truck. Stock everything except i exhaust wrapped the y-pipe.
 
#37 ·
Is it possible that air in the system might cause this after replacing the STC?? Just a thought.
So what I'm getting out of this at this point with what's been found out is that nothing is probably wrong except the random underboost code and its time to crack open the turbo to check to make sure nothng is jammed
Wiped it off
Lol well that's a good problem to have I suppose, although I would have rather we found an "aha!" To know what really happened

Sent from my C6743 using Tapatalk
 
#15 ·
Its stupid because when i R&r the turbo i was really anal. I used 1000grit sandpaper very lightly because there really wasnt much there to take off. I was not abrasive at all. I made sure everything was clean. The VGT looks newer and it says its a garrett (im assuming it got replaced when the turbo did) im going to go and check the wires now.

What about unplugging the VGT. Would that allow me to see if there is a problem with the solenoid? What should it do when unplugged?
 
#16 ·
Lol. It does act wierd though when i get the underboost code. I can describe it as its simular to how the truck acted when i had 2 failing injectors but not nearly as bad. It was randomly miss and buck slightly for differing amounts of time. My wife said it did this for 2 exits on the highway and it has done it for me for about 10 seconds a couple times. Theres nothing that brings it on.

Im nervous because we are about to leave to go out west for the next year to do travel nursing. We are towing a 12,000lb 5er and i just dont was problems because i know it will happen on some mountain pass
 
#18 ·
Earlier today the truck was warm and i pulled out of the driveway. I hit the gas slightly and it missed for a second (didnt hear the normal diesel motor sound, sounded like a car engine) but then ran fine until i was getting on the highway about .5miles away. Where it ran wierd (lost power, missing slightly) for about 5 seconds cleared up and ran fine for the next 25 miles.

I was thinking the VGT was the culprit since its the only value i could find that was slightly out of wack. It did not do this before i removed the turbo and did the stc fitting.

Id keep driving it and not worry about it if i wasent leaving in a month.
 
#19 ·
Il pull the turbo too and see what it looks like. I will let you know what i find later. I appreciate the help. Ive spend the past 8 hours searching forums for a similar problem.

Thank you nighthawk.
 
#20 ·
Side note....from a stop when i go WOT should the tires spin? When i do this i get a lag for a second and then it kicks in and moves but not enough to spin the tires. Is that normal or is that the bottom end lag you are talking about.
 
#21 ·
For laughs and giggles, does your ICP act normally and move fluidly up and down as it should? What are your boost/ebp/icp values when the truck runs rough? What's the IPR doing when the truck runs rough vs. When it runs well?

As to your side note, no, it won't be that snappy with a stock tune and turbo. That's normal. The lag I talk about would be that it wouldn't even spool up until you were around 2500rpm and you'd have a cloud of smoke behind you.

When you pull the turbo and separate the halves, try to move the unison ring and see how free it moves with the vanes before you disassemble further. You could have had no effect on the buildup and were maybe too anal. It would take me a couple days to remove the buildup and rust I see on turbos through my door if I was using 1000 grit only lol.
 
#22 ·
The only thing that seems to act up is vgt when it happens but that would make sense because it the truck it missing vgt is going to change unless vgt is making it do it. With cruise on going on a flat highway it will randomly lose power slightly and the stop and act normal. Let me look at my data logs real quick and see if i find anythong weird with icp
 
#23 · (Edited)
speed: 64mph
boost:1.8psi
RPM:1874
ICP:1005
EBP:3.4
MAP:15.9
VGT:41.4

I think this is when it is doing it. Its hard to tell with soo much data. Its hard to tell if this is where i let off the gas slightly or where it started to act up.
 
#24 ·
previously just before the said blip i got...

speed:64
boost:4.8psi
RPM:1840
ICP:1311
EBP:8.8
MAP:19.4
VGT:50.3
 
#26 ·
K good idea. I just pulled the turbo out and im breaking it open now.
 
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