Low Boost/High EGT

[kikisadventures]

I cannot figure this out for the life of me. I thought I would try posting here before I gave up and brought it to the mechanic.

I have an 2006 6.0 diesel. I'm having a weird issue where when I accelerate, it builds up boost to anywhere from 7-10 psi then dumps it to like 3-4 psi and stays there until I let off the gas. It almost sounds like there is a whistle coming from somewhere when it happens. I also cannot build more than about 10 psi of boost in general. When pulling up a hill I have to drop to about 50 mph to keep my EGTs around 1100. If I try to go the speed limit I'll easily go above 1200.

- I've pressure tested at the intake of the turbo and it holds 30 psi with no leaks.
- I've looked at my MAP tube and it's intact. The MAP sensor seems to be working properly
- I've taken the turbo apart and cleaned and lubed it up
- Verified my VGTs don't ever hit 15% or 85%
- I've tried driving with my exhaust loose to rule out a clogged cat
- I tried to do a exhaust leak check by pressurizing the exhaust pipe. I got rid of most of the leaks. there was still a minor leak between exhaust manifold and turbo y-pipe but it didn't seem that bad.

Here are some reference videos of some of the readings
https://youtube.com/shorts/eE9wIWGJeW0
https://youtube.com/shorts/RkQRQCybR18
https://youtube.com/shorts/6jaAVblMaQI

Does anyone have any thoughts? Any help would be much appreciated. Thanks!

[WhitH]

Sounds like an intercooler related leak to me. Check the seals/clamps on your intercooler pipes.

[ShuttlePilot]

I feel a little gun shy to be offering 6.0 advice as I've been chasing a ghost in mine for over a year now. You didn't seem to mention anything about the Exhaust Back Pressure Sensor (EBP). The reason I bring it up is the EBP often has a huge influence on VGT performance. The pipe that leads to it can get plugged up with soot and it's easy to get to in a van through the dog house. Internet knowledge says the 2003-2004.5's dose not use the EBP information and uses inferred data, but the 2004.5-2010 uses it heavily.

Also do you have AutoEnginuity or ForScan available for a deeper diagnostic look?

-Eric

[kikisadventures]

Originally Posted by WhitH

Sounds like an intercooler related leak to me. Check the seals/clamps on your intercooler pipes.

I made a cap for the turbo intake and pressurized it to 30 psi and didnt have any leaks. Wouldnt that rule out the intercooler?

[kikisadventures]

Originally Posted by ShuttlePilot

I feel a little gun shy to be offering 6.0 advice as I've been chasing a ghost in mine for over a year now. You didn't seem to mention anything about the Exhaust Back Pressure Sensor (EBP). The reason I bring it up is the EBP often has a huge influence on VGT performance. The pipe that leads to it can get plugged up with soot and it's easy to get to in a van through the dog house. Internet knowledge says the 2003-2004.5's dose not use the EBP information and uses inferred data, but the 2004.5-2010 uses it heavily.

Also do you have AutoEnginuity or ForScan available for a deeper diagnostic look?

-Eric

That's something I havent looked at specifically but I do see the EBP increasing with the MAP/boost so I kind of just assumed it was working correctly. That being said I have no idea what the actual numbers are supposed to be.

I do have a different OBD tool that can see more things but it can't command anything

[Twoxentrix]

It's been a good 8yrs now, so hope I'm relaying this correctly; Couple days after I had a new 6.0 engine installed, I was traveling outside of Salt Lake and noticed a significant power drop (like it was only running on 4 cylinders), boost wouldn't go over 7-8, black smoke coming from exhaust while going uphill, and a slight whistle sound like you've expressed each time it began making boost. I drove straight to a Ford Dealer in Salt Lake. Turned out one of the "NEW" rubber Turbo hoses had a manufacturers defect - a slight half-circle tear a little less than 1/2" diameter. You couldn't really see it unless you pressed down on the hose in front of the tear. He even took me back to show me because none of the mechanics had ever seen this happen. Could you have something similar?

[jquevedo]

I have a 2005 6.0 once I had a similar issue, problems with boost, not sure about EGT temperature though, chased my tail for a couple of months, scan devices, computer etc did not offer any great options..
At the end it was a couple fo things EBP, sensor and the Intake air temperature sensor which is a PITA to get to, located in the intake manifold, driver side in the top, need to remove cold air intake to gain access to it, close to the EBP sensor, this air intake temp sensor was clogged seriously clogged with soot, cleaned it and reinstall issue was gone..
Another key is hoses after turbo (elbow) sometimes comes loose or cracks and leak oil, check for oil in the area.

[kbeefy]

I had a whistle like that that was a improperly seated intake boot at the turbo outlet.


I would also be looking at the EBP, it can cause low power but I don't think it would cause black smoke.

[kikisadventures]

So I tried bringing it to a mechanic. They did a smoke test and didn't find any leaks. Their next step was to pull the Turbo and do diagnostics on it. For almost the same cost, I decided to just replace the turbo myself. I had just pulled the turbo a month ago to look at the vanes and there was a fair amount of pitting so it would have had to get replaced sooner or later any. We'll that didn't fix the problem either.

I got to thinking that maybe my initial pressure test wasn't done correctly. I just regulated the compressor and pressurized the intake. But at that low of pressure the flow is so low that maybe I didn't actually get to the pressure i thought i did. So I bought a real test kit and tried it again. I found a few small leaks but no smoking gun. I got up to about 15 PSI and had a normal bleed rate of around 1 psi/sec. I tried driving again and no real change in behavior. Under hard acceleration, the boost just dumps out before i can even get to 10 psi and drains to zero.

I've read this is possible but need to research a little more. A faulty EGR valve can dump the boost into the exhaust. This is what I'm looking at next unless anyone has another idea

[kbeefy]

I don't think the EGR can create a large enough dump to drop the boost more than a couple psi. Unplug the EGR and see if it changes.


Most smoke generators are under 1 psi, they are designed for testing evap systems that can be damaged by pressure. I tried smoke testing the intake on my pickup and it didn't really reveal anything. The boost leak test setup was much more revealing.