2005 6.0L E450 Surging on acceleration.

Patrick_Hamann · November 28, 2012

Bus came in with a blown egr cooler. Diaged and replaced EGR cooler, Oil cooler. Found turbo completely siezed from coolant,worst turbo ive ever seen. replaced turbo assy, did not replace the VGT solenoid. vehicle came back a month later with a lack of power concern, wasnt building any boost, roughly 7 PSI MGP at WOT. found the catyltic converter plugged. replaced cat. Boost now around 19-20 PSI WOT. Watched a few pids, noticed that EBP_G will surge from 31-37 psi, also VGTDC# will also have the same 'sawtooth' pattern. ICP, ICP desired are solid at 3100 PSI wot, no pattern in graph. noticed that EGR pids do not move, Desired pid stays at 0. wont pull to redline, stays around 3000 rpm. Tested fuel system with diesel fuel flow tester at back of cyl. head. pass. 38 psi. no dtcs's present. Removed EBP sensor, found the tube partially plugged cleaned tube. do you guys think that the partially plugged EBP tube could cause this? any help greatly appreciated. it will surge basically anytime, hot or cold.

Matt Saunoras · November 28, 2012

seen a few VGT solenoids surge under load. kind of like a cylical surge under moderate boost

Patrick_Hamann · November 28, 2012

yes it is a cylical surge, comparable to 'trailer hitching' but im going to reinstall the EBP tomorrow and retest. If the VGT solenoid is bad would that show up on the VVT test on IDS/VMM?

Keith Browning · November 28, 2012

Any time I have had surging like that the turbo or the EGR was at fault and typically either one sticking could do it. After verifying your pressure sensors and EGRVP @ KOEO carefully running through pinpoint tests KA should help you diagnose this.

Did you replace the turbo assembly or just the center rotating housing? If you did a CRH did you carefully inspect the unison ring control slot for wear? This will also cause havoc with your air management system.

Posted Image

mchan68 · November 28, 2012

Do you have a spare, known good VGT to swap out for testing purposes? I have had more than my share of trucks coming in lately with failed VGTs causing very low to no boost symptoms. For the relative ease of access, it is worth the time to swap out. For those of you not in the know, I have even used my IPR pigtail connector with the alligator clips that I use to connect to a power and ground source, also to test out VGTs. If you rev the engine to 1200 RPMs steady and power up VGT directly like you would to close an IPR with the same connector, it will achieve the same effect as the test outlined in pinpoint test KA without the need to use IDS.

Keith Browning · November 28, 2012

For those of you not in the know, I have even used my IPR pigtail connector with the alligator clips that I use to connect to a power and ground source, also to test out VGTs. If you rev the engine to 1200 RPMs steady and power up VGT directly like you would to close an IPR with the same connector, it will achieve the same effect as the test outlined in pinpoint test KA without the need to use IDS.

Nice tip Mike! Posted Image

Patrick_Hamann · November 29, 2012

Thanks for the tip mchan, Just an update, Test drove the vehicle this morning, still lacked power, wouldnt build any boost. After it reached operating temp then it seemed like all the power came back and didnt underboost anymore, surging was still present, EGR pids would cycle between 6-100% VGTDC 32-42% under moderate load cruising. went ahead an ran pinpoint test KA. havent removed the VGT actuator yet to watch it move but I will tomorrow. Boost test and EGR test passed on IDS. The VVT test didnt look so good on the graph. It would overshoot each step by quite a bit. but still had the 7 steps. hotline seems to think the turbo is coked/siezed but I have a pretty hard time believing that since it only has 200 miles on the new turbo (this bus sits alot). Unfortunately no one in the shop has a known good VGT actuator to put it so I feel like the next step is going to be removing the actuator and cleaning it. Did notice that if I took active command of VGTDC# the surging would completly stop. I do appreciate the tips, im a new diesel tech and still learning the ropes. Thanks guys

Keith, the whole turbo assembly was replaced

Keith Browning · November 29, 2012

The VVT test didn't look so good on the graph. It would overshoot each step by quite a bit. but still had the 7 steps. hotline seems to think the turbo is coked/seized but I have a pretty hard time believing that since it only has 200 miles on the new turbo (this bus sits alot).

A sticking turbo or a worn unison ring will do exactly that. Remember that sitting is what allows these turbos to rust however since this is a recent replacement the turbo should be treated to minimize this.

Keith, the whole turbo assembly was replaced

Doesn't mean it's good nor does that mean it was properly diagnosed in the first place. Personally, I would TRY a new VGT solenoid and if that is not the problem SPW the turbo... you will still need to take it apart and determine the cause.Strange things can happen. I worked on a truck that was missing one of the turbo mount bolts. So I dutifully dug one up and installed it. Apparently the turbo was not seated or something when it was replaced some time ago and I actually distorted it causing it to seize. Truck had no performance issues when it came in. That's what I got for "fixing" it.

Fordracer · November 29, 2012

I would TRY a new VGT solenoid and if that is not the problem SPW the turbo... you will still need to take it apart and determine the cause.

You need to fix the turbo if possible and not replace it. Got burned on that once. I figured it the customer bought a factory reman turbo you should spw with another factory reman turbo but the whole claim was kicked back. They said I should of fixed the turbo and not replaced it.

Keith Browning · November 29, 2012

You need to fix the turbo if possible and not replace it. Got burned on that once. I figured it the customer bought a factory reman turbo you should spw with another factory reman turbo but the whole claim was kicked back. They said I should of fixed the turbo and not replaced it.

IF POSSIBLE is the key...

Patrick_Hamann · November 30, 2012

I made some progress today, only had about 1.5 hrs to work on it but I removed the turbo and disassembled. found no carbon coking or siezing, carbon was pretty light, unison ring looked good, very -slight- wear on it from the crank pin. went ahead and cleaned it all out per WSM, the shop manual says to put antisieze lube on the unison ring and on the housing (I went ahead and did this but I was always told not to do this by several people) so correct me if im wrong there. I went ahead and powered up the VGT actuator per PPT KA5. sure enough, the valve did not move, even at 100% duty cycle, repeated 10-100% on active command 5 times, finally, I tapped on it with a wrench the valve popped and moved. I cleaned the valve with PM-2 carb tune up cleaner per PPT AK7, tried again, then the valve would move each step. Im thinking this would explain my intermittent underboost and my surging,and it working after it warmed up BUT, I ordered a new VGT actuator and im reinstalling tomorrow and I will let you know how it goes