Exhaust Back Pressure at Idle . Turbo boost spiking

[BrandonOlsen]

X15 CM2350 X114B
Having exhaust back pressure at idle. Doesn’t matter if engines cold or hot. At 700 rpm it’s not very noticeable but you can hear the turbo boost intermittently. At 800 rpm boost goes up to 10. At 950 goes up to 20. When idle reaches 1000 it goes away. Seems as there is a rattle in the valve train (been the way since I bought the truck)

Engine has 660,000 miles. Rebuild at 590,000. Bought it at 640,000. New emissions during overhaul.
I just got insite and have done the rail leak test. 288 drop in 60 seconds. Did the cylinder cut out test and it passed. Just now did a forced regen to make sure it would complete one. Completed regen in about an hour. I have geo tab and it has been showing a constant active regen.
Insite shows no fault codes.
Parts I’ve replaced
Inlet Nox Sensor 11-16-22 due to code 3725
Air filter
Crankcase pressure sensor
Egr Differential Pressure sensor
Dpf differential pressure sensor
Exhaust gas pressure sensor
Intake manifold air pressure sensor

- from egr cooler inlet to the intake I took off all pipes and cleaned them with carb cleaner. I replaced the egr cooler inlet gasket, and all o rings and seals to the intake. Replaced all CAC hoses and clamps.

Exhaust outlet pipe replaced with Part # 5579020 when I first got the truck. 644233
Bellow pipe was replaced as it was leaking and sending smoke into the cab at 655,616

RIGHT NOW.
— after regen truck is idling on its own at 800rpm. Usually always idles on its own at 700. I always bump it up. So with the truck idling by itself at 800 I’m not getting the exhaust back pressure with turbo boost spiking. Bump it up to 900 and still doesn’t do it. No change at 1000rmp. Usually when it idles at 700rpm and I bump the cruise up 1 notch it goes up to 800. Now with it idling at 800, I bump it up 1 notch it only goes to 830.

What do I do next ? Is there a way I can send info from insite to someone to look it over to see if something’s out of line? Appreciate all the help I can get.

-This all started after I got the 3725 code-
I did send in an oil sample and it came back good

[BrandonOlsen]

Shut the truck off for 30 minutes. Turned it back on. Idle at 700 like normal. Bump cruise up to 800. Turbo isn’t boosting. Let it run for a little bit and get back in the truck and idle is back up to 800. Turbo wasn’t boosting but sounded like maybe it was just a tiny bit.

- Was on insite to look at log. When opening it up I got “ A Fuel System Fault has occurred which may cause Trip
Information Data to be incorrect. Troubleshoot fault codes as
necessary, Do not replace the ECM. Resetting the Trip
Information data will clear this message.“

But no fault codes in faults

[Rawze]

(11-28-2022 )BrandonOlsen Wrote:  X15 CM2350 X114B
Having exhaust back pressure at idle. Doesn’t matter if engines cold or hot. At 700 rpm it’s not very noticeable but you can hear the turbo boost intermittently. At 800 rpm boost goes up to 10. At 950 goes up to 20. When idle reaches 1000 it goes away. ...

I don't see an issue with your post much, other than your likely just chasing ghosts.

There are 13+ different engine operating modes inside that ecm.. and if the DPF, SCR unit is not close to 500+F.. then the engine will choke the exhaust manifold + create a bunch of internal engine friction because it has gone into one of its aftertreatment "rapid warm-up" operating modes. Weather and altitude effects this too.

-= The EPA requires the engine to pass emissions as soon as possible after it is started up,.. and it cannot do this until the cans under the truck are up to temperature... hence the different operating modes.

This is also why it will randomly spool up and down the turbo when driving on flat ground.. it is regulating those cans under the truck... changing engine operating modes every few mins sometimes, depends on how cold, etc. it is outside, to do so.

as the system ages.. and sensors read differently over the years the engine will act differently too.. so if you have not done a recent EGR tune-up on it.. then that is the place to start.. and at 600k miles, the egr cooler is likely not flowing as well as it should.. might need to clean it out too.

[windowrattler]

So one of the main goals of the engine is to keep the aftertreatment up to temp. To do this it will "choke" up the turbo to create boost to help create heat. I think I'd take a look at some of the temp sensors in the aftertreatment. Not sure where youre located but it's cold up here so maybe what it is doing is what it actually is supposed to do?

[BrandonOlsen]

(11-28-2022 )Rawze Wrote:  

(11-28-2022 )BrandonOlsen Wrote:  X15 CM2350 X114B
Having exhaust back pressure at idle. Doesn’t matter if engines cold or hot. At 700 rpm it’s not very noticeable but you can hear the turbo boost intermittently. At 800 rpm boost goes up to 10. At 950 goes up to 20. When idle reaches 1000 it goes away. ...

I don't see an issue with your post much, other than your likely just chasing ghosts.

There are 13+ different engine operating modes inside that ecm.. and if the DPF, SCR unit is not close to 500+F.. then the engine will choke the exhaust manifold + create a bunch of internal engine friction because it has gone into one of its aftertreatment "rapid warm-up" operating modes. Weather and altitude effects this too.

-= The EPA requires the engine to pass emissions as soon as possible after it is started up,.. and it cannot do this until the cans under the truck are up to temperature... hence the different operating modes.

This is also why it will randomly spool up and down the turbo when driving on flat ground.. it is regulating those cans under the truck... changing engine operating modes every few mins sometimes, depends on how cold, etc. it is outside, to do so.

as the system ages.. and sensors read differently over the years the engine will act differently too.. so if you have not done a recent EGR tune-up on it.. then that is the place to start.. and at 600k miles, the egr cooler is likely not flowing as well as it should.. might need to clean it out too.

I just did the egr tuneup this weekend. Egr cooler was replaced 70k miles ago as well. I’ll run it and see how it runs now

[BrandonOlsen]

(11-28-2022 )windowrattler Wrote:  So one of the main goals of the engine is to keep the aftertreatment up to temp. To do this it will "choke" up the turbo to create boost to help create heat. I think I'd take a look at some of the temp sensors in the aftertreatment. Not sure where youre located but it's cold up here so maybe what it is doing is what it actually is supposed to do?

Is there a file somewhere that shows what all sensors are suppose to read ? I’m only learning here and have so much to learn. One thing I did notice is it seem like doser stayed on whenever I had insite open

[windowrattler]

For passive regens as Rawze said, it wants to keep it 500 degrees plus. Soot burns off nicely around 1100 degrees. When you are driving around working the truck it will get that hot and burn off.

Passive regens unfortunately never burn off everything. At a certain levels of soot build up the ecm will call for an active regen. This is when the ecm will introduce fuel into the DOC to raise temps up to the 1100ish degrees to clean the DPF filter more completely.

Besides burning off soot exhaust temps for scr need to stay in a window for optimal NOx conversion. Too little temp and the conversion rate suffers and too high of a temperature and it will actually oxide the DEF and turn it into NOx. During active regens and other times of high temps it will stop dosing.

[BrandonOlsen]

(11-29-2022 )windowrattler Wrote:  For passive regens as Rawze said, it wants to keep it 500 degrees plus. Soot burns off nicely around 1100 degrees. When you are driving around working the truck it will get that hot and burn off.

Passive regens unfortunately never burn off everything. At a certain levels of soot build up the ecm will call for an active regen. This is when the ecm will introduce fuel into the DOC to raise temps up to the 1100ish degrees to clean the DPF filter more completely.

Besides burning off soot exhaust temps for scr need to stay in a window for optimal NOx conversion. Too little temp and the conversion rate suffers and too high of a temperature and it will actually oxide the DEF and turn it into NOx. During active regens and other times of high temps it will stop dosing.

Thanks!
What should oil pressure be?
For example... Engine Coolant Temp 182. Engine Oil Temp 188. RPMS 940. Oil pressure 37