VGT Diagnosis & Inspection

Keith Browning · July 15, 2016

I have never had to deal with a turbo fault on a 6.7L until now. The last one turned out to be affected by low oil pressure because the bottom end was coming apart. Anyway, it's a 2011 cab and chassis with a single stage turbo. The truck runs okay but during moderate to heavy acceleration the turbo over boosts then the check engine light comes on and the engine derates.

DTC P0234 in memory, fails KOER for insufficient EGR flow which makes sense if the turbo is not working.

I go through pinpoint tests KA. The pressure sensors check ok. Commanding the turbo does absolutely nothing - there is no change in EBP or MAP at all. After removing it, the VGT actuator buzzes when ramped up and valve movement is visible along with increased resistance on the tip when the duty cycle is increased. It seems to be functioning properly. The PCED directs you to clean the actuator and reinstall it and re-evaluate. If the concern is still present then replace the actuator. If the concern is STILL present then hang a turbo on the engine. I think I am wasting my time with this actuator.

Is there a way to inspect the turbo itself? Has anyone ever messed with this? If I remove the plug on top and try to move the piston and the vanes I get no movement at all but I don't know if that is even possible to do. I would think the oil would drain from both sides of the piston but how much resistance should be expected? I am thinking not and that is the reason why Ford has you spend so much time playing with the actuator.

Has anyone seen one of these turbos lock up the vanes?

Brad Clayton · July 15, 2016

The best way to check for freedom in the vane movement area is to remove the side piston plug or just push the plug itself. The one in the photos already had the oil drained out but I am thinking it shouldn't take much effort to push that rack inwards. I haven't seen a stuck vane situation on one of these yet, but I am sure they are out there.

These first three photos can only be of use with the VGT solenoid installed and being actuated with the scan tool, then the rotary movement of the elliptical cam can be measured for the slight up and down movement or visually inspected for movement all together.

Jeff_ · July 15, 2016

I think you're on the right track Keith. I have only had one turbo with seized vanes on a 6.7 and it set a P0234.

forddieseldoctor · July 15, 2016

I had one under warranty that hotline said was probably intermittent sticking vanes. Stuffed a turbo on it and it fixed it. I don't remember the code or the year. Just that it was on a pickup. But in this case I agree it's probably sticking.

Matt Saunoras · July 17, 2016

In that last pic take your magnet tool and pull the piston in and out to feel for binding. That will run the cam, unison ring and vanes in their full direction of travel. 6.0s are the same way, I don't believe it's possible to remove the piston completely or jump teeth because the unison ring will only allow so much cam travel

Keith Browning · July 22, 2016

Well to update this - when I got the turbo on the bench I checked it out better. The vanes are stuck solidly. Would not budge. The only movement I had was between the rack and the cam about 2 or 3 mm. Seems like getting these turbos out is getting harder and harder. I spent at least an hour alone trying to get the down pipe out and getting the clamps to come off the pipes at the turbo. The left manifold clamp on the bottom needed a few hours of soak time with some Blaster oil before it would let go. :hammer: