Cummins ISM not reading boost correctly?

[Mikesuburban1]

Hi all i know you mostly talk about the isx but i figured someone on here could help me. Soo the truck is a 07 IH 7600 with ism@425hp no dpf. New turbo new egr, manifold pressure sensor, intake temp sensor, egr temp sensor. All new parts have maybe 1000 miles on them. Now the truck is sluggish my scangauge reads 31.5lbs boost but my mechanical gauge reads 35-38lbs boost but once in a while the computer will read 38lbs and the truck pulls like it should but then goes back to 31.5lbs. What can be causing this? It has a new manifold pressure sensor could it possible be a ecm problem? Any advise would be much appreciated [/size]

[Nilao]

Sensors can be faulty right out of the box. It could also be some corrosion on the connector or a wiring issue.

[in2trux]

Did you replace the turbo actuator too? A sticky actuator or the air valve that controls it can cause these symptoms and is many times the problem, not the turbo. It could be going into silent derate.

Did you replace or thoroughly clean the egr valve? Sticky egr will cuase this problem too.

[Mikesuburban1]

(02-24-2017 )in2trux Wrote:  Did you replace the turbo actuator too? A sticky actuator or the air valve that controls it can cause these symptoms and is many times the problem, not the turbo. It could be going into silent derate.

Did you replace or thoroughly clean the egr valve? Sticky egr will cuase this problem too.

I replaced the egr with a new one and the new turbo came with a new actuator. I have a mechanical boost gauge that i tapped into the intake horn right before the manifold. The turbo seems to spool fine the boosst gauge reads 38lbs but the sensor and ecm are reading 31.5lbs and sometimes it will read correct and power comes back

[in2trux]

Scan gauge boost is electronically calculated, not actual.
Did you replace delta P (pressure differential sensor?)? The one with 2 tubes on the intake manifold.
Those tubes are notorious for clogging on the Isx and Ism. You can't clean the sensor, only replace.
It's a key sensor and can throw ecm function. Does it cough or sneeze? I don't know how else to describe it,
thats what it sounds like, very quick interruption in power. Some call it turbo cough.
I had that problem with the Ism I use to run, egr tune up cured it.

While your at it, exhuast gas pressure sensor should be replaced too.
They're about $80-90.
Other than that I would check for leaks in CAC that my be showing at high boost.

[Mikesuburban1]

(02-24-2017 )in2trux Wrote:  Scan gauge boost is electronically calculated, not actual.
Did you replace delta P (pressure differential sensor?)? The one with 2 tubes on the intake manifold.
Those tubes are notorious for clogging on the Isx and Ism. You can't clean the sensor, only replace.
It's a key sensor and can throw ecm function. Does it cough or sneeze? I don't know how else to describe it,
thats what it sounds like, very quick interruption in power. Some call it turbo cough.
I had that problem with the Ism I use to run, egr tune up cured it.
I put new exhaust back pressure sensor and made no difference. Removed one end of the cooler and exhaust flows good. Took the diff tubes off and cleaned them they really werent that dirty. Removed delta p sensor and it wasnt clogged or anything but there was moisture in it is that normal? I have a buddy coming over tomorrow with his insite is there anything i should be looking for with the sensors?
While your at it, exhuast gas pressure sensor should be replaced too.
They're about $80-90.
Other than that I would check for leaks in CAC that my be showing at high boost.

[Mikesuburban1]

(02-24-2017 )Mikesuburban1 Wrote:  

(02-24-2017 )in2trux Wrote:  Scan gauge boost is electronically calculated, not actual.
Did you replace delta P (pressure differential sensor?)? The one with 2 tubes on the intake manifold.
Those tubes are notorious for clogging on the Isx and Ism. You can't clean the sensor, only replace.
It's a key sensor and can throw ecm function. Does it cough or sneeze? I don't know how else to describe it,
thats what it sounds like, very quick interruption in power. Some call it turbo cough.
I had that problem with the Ism I use to run, egr tune up cured it.
I put new exhaust back pressure sensor and made no difference. Removed one end of the cooler and exhaust flows good. Took the diff tubes off and cleaned them they really werent that dirty. Removed delta p sensor and it wasnt clogged or anything but there was moisture in it is that normal? I have a buddy coming over tomorrow with his insite is there anything i should be looking for with the sensors?
While your at it, exhuast gas pressure sensor should be replaced too.
They're about $80-90.
Other than that I would check for leaks in CAC that my be showing at high boost.

New exhaust sensor. Clean delta tubes they werent cloged and egr is not clogged exhaust flows good. Delta p sensor was not clogged but had moisture in it could that be somthing?

[Mikesuburban1]

(02-24-2017 )Mikesuburban1 Wrote:  

(02-24-2017 )in2trux Wrote:  Scan gauge boost is electronically calculated, not actual.
Did you replace delta P (pressure differential sensor?)? The one with 2 tubes on the intake manifold.
Those tubes are notorious for clogging on the Isx and Ism. You can't clean the sensor, only replace.
It's a key sensor and can throw ecm function. Does it cough or sneeze? I don't know how else to describe it,
thats what it sounds like, very quick interruption in power. Some call it turbo cough.
I had that problem with the Ism I use to run, egr tune up cured it.
I put new exhaust back pressure sensor and made no difference. Removed one end of the cooler and exhaust flows good. Took the diff tubes off and cleaned them they really werent that dirty. Removed delta p sensor and it wasnt clogged or anything but there was moisture in it is that normal? I have a buddy coming over tomorrow with his insite is there anything i should be looking for with the sensors?
While your at it, exhuast gas pressure sensor should be replaced too.
They're about $80-90.
Other than that I would check for leaks in CAC that my be showing at high boost.

New exhaust sensor. Clean delta tubes they werent cloged and egr is not clogged exhaust flows good. Delta p sensor was not clogged but had moisture in it could that be somthing?

[in2trux]

There is a good amount of condensation at the egr but the Delta P should be dry.
If it is wet and hasn't been replaced, moiture isnt going to help anything.
If you haven't replaced it, I would. Next is figuring out where the excess moisture is coming from, possibly leaking egr cooler?
When you get it on insite, make a note of voltages and values of key sensors.
You might pm gearhead or Unilevers for more help or remote tuning.
I found the Ism to be very stable and reliable and is my 1st choice for class 6 or 7.