Overboost PO234 issues

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

I've searched for this and come up with some things that I've tried but nothing that has seemed to work for me so i figured I'd maybe post this for other ideas or maybe I'm just missing something in general. Last April i purchased a 2005 CRD with 120k on the clock. I'm the 3rd owner and the last owner installed a GDE eco tune and transmission tune as well. I didn't have any issues with it for a while but this past winter it threw the overboost code. It had thrown this code one other time but i did the italian tune up and it went away for a while. This time it will not and inspection is coming up soonish so i'd like to get the issue licked ahead of time.

What i have done so far:
Inspected and carefully cleaned the MAP sensor. It was gummed up a fair amount but it came clean but did not clear the CEL.

Checked to make sure the turbo vane actuator arm moved freely. It was tight at first but i worked it and actually got it to move very freely with just a little work.

I replaced the turbo inlet hose at the time of checking the vane actuator arm due to it tearing.

My thoughts are: It could possibly be a charge hose. The turbo to intercooler hose has a fair amount of oil soak right at the compressor inlet where it clamps. Although i must say i believe these hoses are Samcos? I could be wrong but they appear to be all silicone construction so i'm not sure if i'm getting a leak here or not. Would this even cause an overboost situation? After working the turbo vane actuator the sound of the turbo changed significantly. Under load at around 2000 rpms i can definitely hear the spool of the turbo and before it wasn't as noticable. That is was made me consider a possible boost leak at the hose itself. Again though i dont see how that would cause an overboost situation. I guess the MAP sensor itself could just be bad?

gmctd · **Posted:** Sun Jan 25, 2015 8:10 pm

Try working the vane actuator more - may be sticking partially closed, allowing more Boost than desired

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

I can try that however the arm had pretty good movement up and down. Gotta try something I suppose though.

greiswig · **Posted:** Mon Jan 26, 2015 2:24 pm

Do a search for my username and overboost. Movement at the actuator can be deceptive.

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

I did a search and did find some info i suppose. I guess maybe could you elaborate? I checked it again today with it at idle and reached my hand down to the actuator and unplugged the vacuum hose to feel the rod fall and then raise back up. It feels like its moving very freely and around 1/2 inch of movement im guessing just from the hip. I would guess that if the boost pressure sensor was bad altogether the jeep would run terrible and honestly that isn't the case at all. I really don't want to go removing the turbo if it isn't an issue with the turbo vanes being free or anything like that since it would be somewhat involved and i don't have a ton of time at the moment. Am i not seeing something? perhaps i'm doing something wrong? I only know what i've read here basically but maybe i'm not understanding something right. Unless there is supposed to be more movement of the vane actuator which i suppose is possible...... but without the diaphragm attached i was able to move the rod i'd say at least an inch up and down vertically. Perhaps a video is in order?

gmctd · **Posted:** Mon Jan 26, 2015 7:19 pm

Full vacuum = full Boost

ECM pulses the Vacuum Regulator Solenoid to control Boost levels by venting vacuum as necessary
- could be the solenoid shuttle is stuck, preventing the vent function
- could be the vent filter dangling beneath the solenoid is plugged, same result

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

Thank you. This helps me a lot actually. I'll continue to troubleshoot tomorrow.

gmctd · **Posted:** Tue Jan 27, 2015 12:24 pm

Irocelectric93 wrote:

Thank you. This helps me a lot actually. I'll continue to troubleshoot tomorrow.

Almost fergot: welcome to the forum, and, if you have not, read thru this, where you will find a link to the downloadable '05 and '06 KJ Field Service Manuals
viewtopic.php?f=5&t=54207

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

Here's a video. My first video ever so forgive the redundancy and whatnot. http://youtu.be/EuSOaDEiL_I

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The control rod is moving fine. As long as the internal link to vane control ring is not failed, I would think the turbo is fine. Maybe the EVM controlling the turbo is leaking (rubber blue isolator and air filter on bottom) and not fully opening the vanes under high load. Make sure there are no air leaks in the boost system during reassembly. An air leak on the charge side typically leads to an underboost and an overspeeding turbo is the leak is small.

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

Is there a way to check the operation of the vacuum generator or whatever exactly its called? I know all my boost hose connections are tight however as stated before there is oil residue on the hose at the turbo although it does appear to be a silicone hose.

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

I did test the boost solenoid today btw. It ohmed out to 29 ohms and i ran some wires to it to hear it change states. It didn't click as loud as i would have liked to be honest but it did click. I blew through the orifices and the vent to atmosphere which is guess is its normal state seemed open to me as in i was getting air out of it relatively easily. Now the EVM... i dunno esp under load as suggested. is there a way to check the vane linkage without removing the turbo? I don't know how hard it is to remove the compressor housing from the cartridge if its even possible with the turbo still mounted. I honestly didn't really look. I did double check my charge hose at the intercooler which was the only place i could have possibly seen it leaking by. I really should put t bolt clamps or constant torque clamps on to be honest. I didn't check the charge pipe from the intercooler to intake yet but i'll probably do that tomorrow just to be sure. I don't want to start just throwing parts at this thing but i may get to that point. I did order the programmer tool from GDE just so i could read codes and what not which will be nice to have.

Irocelectric93 · **Joined:** Sun Jan 25, 2015 5:59 pm **Posts:** 60

ok well after receiving the GDE programmer tool i was able to read the code on my time. The only code showing up this time is a P0671 which apparently it the number one glow plug. So after a day of driving the overboost code still hasnt came back. So that is good news. I'll need to address the glow plug either by replacing it or whatever. I do know that the gentleman who had the Jeep before we did replaced all 4 glow plugs right before he sold it to us. I believe he used the 7volt ones ordered from IDparts.com. At any rate now might be a good time to do the intake pipe upgrade i've seen out there? Thanks for the help and explanation on how the boost system is actually controlled. Now to fix the next issue......

ebbnflow · **Posted:** Sun Feb 01, 2015 2:20 pm

There was a bad batch of Etecno 7v glow plugs that made it to end users last year. I had 3 out of 4 of my etecnos die within 6 months of service in sunny California. Id parts was great about warrantying them, but I never like doing the same job twice.

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

Irocelectric93 wrote:

I'll need to address the glow plug either by replacing it or whatever. I do know that the gentleman who had the Jeep before we did replaced all 4 glow plugs right before he sold it to us. I believe he used the 7volt ones ordered from IDparts.com. At any rate now might be a good time to do the intake pipe upgrade i've seen out there? Thanks for the help and explanation on how the boost system is actually controlled. Now to fix the next issue......

Since there was a batch of Etecno 7V plugs failing prematurely, I'd suggest you replace all 4 at the same time, or risk doing the job multiple times. The factory elbow has to come out to replace most of the plugs, and it is a huge pain to remove and install. Once you do that job once, you won't want to do it again. :banghead:

Our intake elbow kit is designed to vastly improve access to the glow plugs.

Overboost PO234 issues

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