2005 Liberty CRD Overboost and insufficient EGR flow

jhnbrns · **Joined:** Wed Jan 11, 2017 8:57 pm **Posts:** 10

With the rebuilt injectors, new boost hoses, snorkel, MAP, EGR valve, EGR gaskets, EGR Exhaust pipes, timing belt, water pump, thermostat, vacuum controls ... Now the car has poor acceleration just above idle. It produced codes P0234 Turbo overboost, P0401 EGR Flow insufficient - detected, P2141, EGR throttle control circuit A low. Is this aa simple as a sticking EGR flow control valve? I've cleared the codes and can drive fine if I wait till the rpm gets above 1800, then I have strong acceleration. Thoughts?

joe_ · **Posted:** Mon Apr 03, 2017 8:39 pm

Anything with "control circuit low" generally means something is shorted to ground. The turbo overboost may mean that the vanes in turbo are stuck, or something to do with the vane vacuum actuator solenoid or MAP sensor. Actually P0234 means "Boost Pressure Sensor Negative Deviation"; I might be misunderstanding that, but I'm reading it as underboost rather than overboost.

First thing I would do is check for wiring rubbing on something. Common places are behind the fuel filter head bracket and on the bracket that connects from the alternator to the intake.

flash7210 · **Posted:** Mon Apr 03, 2017 9:27 pm

Sounds like a under boost problem.
Could be:
Dirty or bad map sensor
Stuck open egr valve

Best thing to do is just block off or delete the egr.

jhnbrns · **Joined:** Wed Jan 11, 2017 8:57 pm **Posts:** 10

Thanks for the help. I'm able to drive easy below 1800 rpm and not get any DTC so this is an intermittent problem. Intermittent P2141-EGR AIR FLOW CONTROL VALVE SHORT TO GROUND doesn't make much sense, but the P0401 - insufficient EGR flow and P0234-BOOST PRESSURE SENSOR NEGATIVE DEVIATION sounds like the boost air and EGR and not right below 1800 rpm. Would a failed Flow control valve have a constant DTC?

flash7210 · **Posted:** Wed Apr 05, 2017 8:37 pm

Yes, a failed FCV will result in a constant CEL.
Maybe its just a loose connection?

I wouldnt bother getting a new FCV.
Maybe you can find a used one one ebay.
Or even better, load one of the free DIY tunes and see if that makes the code go away.

jhnbrns · **Joined:** Wed Jan 11, 2017 8:57 pm **Posts:** 10

Thanks for the clues. I suspect my liberty CRD performance issues and intermittent P0234, P2141 and P0401 during quick acceleration from a stop where caused by the EGR flow control valve stuck open or at stuck at idle position. Other symptoms besides the codes and rough acceleration from a stop, were a completely shudder free shutdown, and I couldn't hear the valve open when I turned the engine off. I checked that the valve was energized(audible buzz) and open when engine was off (key in on position). The valve had resistance when I attempted to move it to closed position so the gears are ok. I disconnected the harness and reconnected. After all that, the performance has been better and the engine sounds much more smooth during acceleration and low speeds. I can now hear the valve close when I turn the engine off. I'll be more sure after a week of driving and i'll update this post.

WWDiesel · **Posted:** Sat Apr 08, 2017 12:14 pm

Do your engine and yourself favor and either block off the EGR feed tube or install a Weeks Elbow Kit (SasquatchParts.com)!

If you block off the EGR Feed Tube, you can remove the butterfly flapper from the FCV and trash it!

EGR Block off plate dimensions & install instructions:> http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=76576

Problem solved forever!!! :wink:

jhnbrns · **Joined:** Wed Jan 11, 2017 8:57 pm **Posts:** 10

A few months later, the liberty CRD (165K miles) now has P0299 underboost just above idle. After removing the three bolts of the boost control, the variable vane actuator has a step or bump midway through the actuation. So I suspect it is sticking slightly while driving. Has anyone rebuilt the turbo or at a minimum cleaned. What's involved with separating the turbine and pump housings to get to the variable vanes? Gaskets?

There are no CAC leaks, air/fuel filters are new, FCV and EGR are good, up to 35 PSI boost with normal acceleration to 60 mph. Less than 1/8" play at the turbo - pump.

Please help

mass-hole · **Posted:** Tue Aug 01, 2017 8:14 pm

I recently posted a tear down of the turbo that should give you an idea of how it's put together, it's only like 5 bolts to remove the turbine housing from the center section but they might be tough to get to on the jeep.

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jhnbrns · **Joined:** Wed Jan 11, 2017 8:57 pm **Posts:** 10

Thanks. Looks like I won't need to separate the rotors but just clean up the turbine housing carbon. Did it go back together ok?

mass-hole · **Posted:** Wed Aug 02, 2017 6:06 pm

jhnbrns wrote:

Thanks. Looks like I won't need to separate the rotors but just clean up the turbine housing carbon. Did it go back together ok?

I never put it back together, it was a spare I pulled apart.

2005 Liberty CRD Overboost and insufficient EGR flow

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