CRD overboost problem! - JeepForum.com
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post #1 of 4 Old 09-08-2019, 08:52 PM Thread Starter
caddydaddy
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CRD overboost problem!

I'm having trouble figuring out why I keep getting an intermittent overboost condition on my CRD. I've replaced the actuator which made no difference, and using my BlueDriver to log data, it's showing a max of 37 PSI! I definitely hear air noises when it does this and the engine falls flat on its face, doesn't accelerate and just holds an RPM, unless I back off the throttle. Then the red lightning bolt light comes on and there's barely any boost because it's in limp mode.
Looking at the data, sometimes the fuel rail pressure drops very low. One time at 14.5 PSI of boost, the rail pressure read only 46 PSI! The max pressure was 23,872 PSI at WOT, so the HP pump seems to be capable of the correct pressure.
The lift pump and fuel filter are new, but it's still having the same issues. It's also smoking when idling, I think it has one or more leaking injectors. Not sure if that would add to this issue or not.

Any help is appreciated!


2007 CRD Limited w/QDII
GDE HOT Tune, Turbo Resonator Delete
2" RC lift
225,000+ miles!
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post #2 of 4 Old 09-11-2019, 11:46 AM
japeart
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Check to make sure the sensor in the filter box is seated fully. I had something like this happen, thought it was the actuator but turned out to be that sensor. Throws the boost reading off. Jeep thought I was making almost 30psi.

07 Grand Cherokee - 3.0L CRD - GDE Hot Tune - QDII - OME HD - 255/80/17 Nittos
Black WK Club #156
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post #3 of 4 Old 09-11-2019, 10:21 PM
rokrau
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Quote:
Originally Posted by japeart View Post
Check to make sure the sensor in the filter box is seated fully. I had something like this happen,
You mean the Mass Air Flow sensor in the Air Filter box?
That’s interesting. I get overboost sometimes when the temp drops below 40F.

--Roland, 2008 Grand Cherokee Overland, 3.0 CRD, EHM and TRD
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post #4 of 4 Old 09-12-2019, 12:36 AM
japeart
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No, the mass airflow is on the outlet.there is a pressure sensor on the filter housing itself. It is in front of the coolant tank.

I believe it measures atmospheric pressure. So if it is disconnected or loose like mine was it seems to register as 0 psi atmospheric. Which means the computer doesn't subtract atmospheric pressure from the boost reading and thinking the boost is way higher than it is.

I may be wrong on how it exactly works, but that pressure sensor was my problem.
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07 Grand Cherokee - 3.0L CRD - GDE Hot Tune - QDII - OME HD - 255/80/17 Nittos
Black WK Club #156
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