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Old 07-29-2014, 04:20 PM
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Boost Issues

I made a couple of posts in someone elses thread but didnt want to hijack it too bad so I am starting a new one.

My truck is not producing as much boost as it used to and the turbo seems to lag more than it used to on initial acceleration. I am also seeing (much) more black smoke if I try to accelerate hard from a stop and occasionally I see a puff of smoke when I try to accelerate at highway speeds. I am also starting to notice more of a rumble sound from the exhaust instead of the jet fighter/blow drier hybrid sound that I am used to. Under normal driving conditions (normal for everyone else) I probably would not even notice the differences but the way I drive I can certainly tell the difference.

The first thing I though were sticking vanes in the VGT. I took it apart over the weekend and gave it a good cleaning. There was virtually no rust and very little carbon/soot buildup - just enough to get my hands really dirty but not enough to cause anything to bind. All of the parts looked good - unison ring was not worn, vanes would freely move but were not sloppy, bearings felt fine, etc. I got it all cleaned up and back together but it didnt really make a difference.

I am able to hook my AE up to the truck to cycle the VGT and I can hear the pitch of the turbo change so I know it is working (at least partially) and responding to commands from the ECM. Today I added a few more PIDs to my Scan Gauge (EBP, VGT, and MAP) so I could easily watch the numbers as I drove around. KOEO EBP and MAP are within .5 psi. KOER at idle the MAP is about 15 - 15.5 psi and the EBP is about 17 - 18 psi. Driving the EBP would climb up to about 50 psi but I never saw it go over that. VGT never did go outside of the 15% - 85% range - from what I could tell it usually stayed in the 40-50% except when I would go WOT or back to idle and it would go up or down. Boost gauge (OEM in the dash) is not going above 22-24 psi where it used to hit 28-30 easily. It is also slowly droping to about 20 psi as RPMs increase, when the truck shifts into the next gear they will climb back up and drop again as RPMs climb. I am also noticing that EGTs do not seem to be quite as high as they used to be - under heavy load, like merging into interstate traffic, it was not that uncommon for EGTs to get in the 1350-1400 range for a few seconds until I let off. Now they seem to be staying in the 1100 - 1200 range under the same heavy load.

About the only thing I have not done is pressure tested the charge air system. I plan on doing that this weekend but I am not sure if that will be the issue. I can see where it would cause the slow boost/low boost issue but would it cause the rumble I am hearing in the exhaust at idle? I am leaning toward the VGT actuator/solenoid purely because of the different sound at idle and the fact that I have already cleaned the turbo and the vanes did not appear to be sticking.

About the truck: 2006 F250, 170k miles, 4x4, automatic transmission, 4" turbo back AFE exhaust, EGR delete, Atlas 40 FICM tune, 58v FICM upgrade, SCT canned performance tune (I know, I have already paid for a custom tune but I want to get this issue resolved before I flash it).

If anyone has any suggestions I am more than willing to try them! I dont like the idea of throwing parts at something until it gets fixed. I certainly dont like that idea when we are talking about $900+ turbos!

Also, sorry for the long post but I am trying to give as much information as possible right from the start.

Last edited by BrianSnelgrove; 07-29-2014 at 04:24 PM.
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  #2  
Old 07-29-2014, 04:45 PM
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Good post with some good preliminary diagnostics on there. Sounds like you've done some research on this before.

Your issue does sound like a turbo/boost issue. It hasn't logged any codes? What does KOEO and KOER test do? Does it log any codes after the test?

Normally black smoking is caused by turbo or EGR issues. Seeing as you have an EGR delete it can't be something with that. Off the top of my head it sounds like a possible issue with the EBP sensor. Have you pulled the sensor and blown through the tube? I've seen some goofy boost issues caused by a plugged up EBP sensor tube.

Pressure testing the intake side isn't a bad idea either though. Have you inspected the exhaust side turbo Y pipes and made sure you don"t of't have any sort of leaks there?
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Old 07-29-2014, 05:38 PM
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I've had this 6.0 four about 4 years, I've researched all kinds of issues!

When I had the turbo off last weekend the only soot residue was on the downpipe and it was a very small amount. i didn't see any soot on the firewall, uppipe, or the connection between the uppipe and turbo. While I have not pulled the EBP tube off yetI don't know if that is the problem, the scan gauge shows a quick PSI change as I accelerate and decelerate but I will certainly pull it off and check it.

The only codes i saw were FICM performance codes. I think those are related to the 58v FICM so i was not really concerned about them. I haven't run the KOEO or KOER tests yet but I will and post the results.
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Old 07-29-2014, 06:19 PM
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The only code before the KOEO/KOER test is P0611 - FICM Performance. I reset the codes and ran both the KOEO and KOER tests. KOEO brought the P0611 back. KOER found P1703 - Brake Switch Out Of Test Range.

I brought up the data meter in AE and started looking at the EBP. EBP Absolute is about 20 psi but desired is about 5 psi - they are fluctuating slightly - and the VGT duty cycle is about 77%. Does that sound right? Is either AE or the ECM adjusting for barometric pressure in the desired EBP?

If I let the truck sit and idle for a few minutes and sometimes the VGT duty cycle slowly climbs up to 85% while other times it hovers around 66%. I can cycle the VGT using AE and there is definitely a difference in the sound of the exhaust and the EBP drops slightly.
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Old 07-29-2014, 11:49 PM
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Your engines breathing

Lets see if I can keep this simple. When you are talking about boost your talking about how your engine is breathing. It inhales and exhales just like you do.

To do that the pcm compares several sensors not just one. Inhale it compares Mass air flow; Map;Iat. Exhale is EBP. It compares all of these to tell the VGT what to do, whether to breathe faster or slower to give the right oxygen content to support the combustion process.

You may have COPD or double phnumonia.
EBP issues can be a biased sensor, plugged tube or actual restriction in the exhaust system. If your system is too restricted the engine can't exhale and it will smother and die.

You need to determine which one is doing what.
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Old 07-30-2014, 03:03 PM
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Quote:
Originally Posted by dannyboy950 View Post
Lets see if I can keep this simple. When you are talking about boost your talking about how your engine is breathing. It inhales and exhales just like you do.

To do that the pcm compares several sensors not just one. Inhale it compares Mass air flow; Map;Iat. Exhale is EBP. It compares all of these to tell the VGT what to do, whether to breathe faster or slower to give the right oxygen content to support the combustion process.

You may have COPD or double phnumonia.
EBP issues can be a biased sensor, plugged tube or actual restriction in the exhaust system. If your system is too restricted the engine can't exhale and it will smother and die.

You need to determine which one is doing what.
Haha that's funny right there! Good way to describe it though.

To the OP, your numbers sound decent. I'm guessing the difference you're seeing on EBP desired and actual is because the desired is not reading the atmospheric pressure. KOEO EBP should be around 14.6-15psi. So if you're at 20psi actual EBP it's really only around 5 psi when you subtract atmospheric pressure, which would match with desired EBP.

I'd still make sure the EBP sensor tube is clear. It's a pretty quick thing to check. I've seen some really weird boosting issues caused by a goofy biased EBP reading.

Also make sure you don't have any exhaust or boost/intake leaks going on as well.
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Old 07-30-2014, 05:49 PM
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Thank you danny and justin.

Just a quick update - I have driven the truck about 45 miles with the scan gauge hooked up and the numbers seem to be really consistent - nothing really goes out of whack or goes too far off of what I believe normal to be. But I have noticed that my fuel mileage has dropped. My truck has never been one of those that claim to get 20+ mpg but it usually averages around 14ish. Looks like it has dropped to about 11-12 over the past week or so.

I am going to pull the EBP this weekend and make sure the tube is clear then double check for any intake/exhaust leaks.

Thanks for the help and I will keep yall posted.
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