Have no clue what's really wrong.

[Copper]

Hello everyone, I am having quite a hard time figuring out what is wrong with my truck. It currently has an engine protection torque derate that won't clear no matter what I try.

Insite says it's caused by two IMAP sensor fault codes. Both of which say I have low manifold air pressure. I have replaced the IMAP sensor two times with Cummins OEM sensors.

This problem started after my previous turbo went bad and started pissing oil into my intake manifold. I have since replaced my Turbo with a reman from yts with actuator.

I have replaced my intercooler boots and made sure all my clamps are as tight as possible. I have not pressure tested the CAC as I do not have that tool. Is this likely to be my problem?

I do have positive pressure coming out of the IMAP sensor install hole at Idle.

I am at a loss as to what to do next. And after being down for a month and a turbo replacement. I'm running a little low on funds. Any help and guidance you can give me would be greatly appreciated. Thank you all for your time and help.


Truck Info

2015 Freightliner cascadia
Isx15 cm2350
Engine serial number 79729107
Not De-mandated

Current Codes: 3714, 0125, 4616

[MommaBurt]

I would check the other sensor values off the bat. Sensors like barometric pressure, turbo speed, and exhaust back pressure. Really, you should check all of them. I would also double check that you got the correct IMAP sensor for your truck. It's more of a lack of charge flow code than a lack of boost pressure code. I can PM you more info if you'd like.

[Rawze]

(10-18-2023 )Copper Wrote:  ... previous turbo went bad and started pissing oil into my intake manifold...

just some FYI:
almost always, turbo bleeding oil into the CAC is caused by excessive crank case pressure buildup. #1 cause = not changing the crank case filter often enough. Better yet, someone can prevent this by replacing the crank case filter with a maintenance free one like shown here ...
ref: http://rawze.com/forums/showthread.php?t...50#pid8950

And yeah, you need to do a proper CAC/intake pressure tests to ensure your CAC does not leak down from 30-PSI to less than 20 PSI on one minute.

Also, if the exhaust is clogging up, it will starve the intake of air and cause turbo speed derates.

You need to also ensure that you are plugging the the IMAP sensor all the way into the herness connector firmly before putting it into the hole where it mounts. If your installing the sensor first, then trying to plug it in, it will often not plug in all the way.

Lastly.. don't rule out that the replacement turbo is not damaged. You might want to have the exhaust turbine blades checked (only way to check them fully is to remove the exhaust housing of the turbo) by a turbo shop to ensure the outer edges of the exhaust blades are not damaged.

If that EGR cooler is old, they are known for spitting random carbon chunks out, and damaging exhaust blades of turbo and making it have weak boost. I have seen people go thru 3 or 4 turbo's before figuring this out. It is a common issue with older trucks that are not deleted .. or even if they are deleted, and there is no block plate between manifold and egr cooler to prevent it.

[Colter]

How much oil was pushed? Have you cleaned out the charge air cooler? Air filters clean?

Pressure test the cooler itself and confirm no leaks, check all sensors mentioned.

Monitor your manifold pressure under different conditions just to make sure its value is changing, there's a quite slim chance of a wiring problem that has the sensor value reading but stuck in range.

[Copper]

(10-18-2023 )MommaBurt Wrote:  I would check the other sensor values off the bat. Sensors like barometric pressure, turbo speed, and exhaust back pressure. Really, you should check all of them. I would also double check that you got the correct IMAP sensor for your truck. It's more of a lack of charge flow code than a lack of boost pressure code. I can PM you more info if you'd like.

Yes if you wouldn't mind PM any info you think is relevant. What is the appropriate ranges for all the sensors? Dumb question, but can you explain the difference between charge flow and boost pressure?

[Copper]

(10-18-2023 )Rawze Wrote:  

(10-18-2023 )Copper Wrote:  ... previous turbo went bad and started pissing oil into my intake manifold...

just some FYI:
almost always, turbo bleeding oil into the CAC is caused by excessive crank case pressure buildup. #1 cause = not changing the crank case filter often enough. Better yet, replace the crank case filter with a maintenance free one like shown here ...
ref: http://rawze.com/forums/showthread.php?t...50#pid8950

And yeah, you need to do a proper CAC/intake pressure tests to ensure your CAC does not leak down from 30-PSI to less than 20 PSI on one minute.

Also, if the exhaust is clogging up, it will starve the intake of air and cause turbo speed derates.

You need to also ensure that you are plugging the the IMAP sensor all the way into the herness connector firmly before putting it into the hole where it mounts. If your installing the sensor first, then trying to plug it in, it will often not plug in all the way.

Lastly.. don't rule out that the replacement turbo is not damaged. You might want to have the exhaust turbine blades checked (only way to check them fully is to remove the exhaust housing of the turbo) by a turbo shop to ensure the outer edges of the exhaust blades are not damaged.

If that EGR cooler is old, they are known for spitting random carbon chunks out, and damaging exhaust blades of turbo and making it have weak boost. I have seen people go thru 3 or 4 turbo's before figuring this out. It is a common issue with older trucks that are not deleted .. or even if they are deleted, and there is no block plate between manifold and egr cooler to prevent it.

The truck does have the maintenance free filter. Is there anything else that can cause high crank case pressure?

the truck seems to regen fine. Is it still possible the exhaust/aftertreatment is clogged somehow?

Thank you Mommaburt, Rawze, and Colter for responding.