Rawhide1205

Hi everyone, having a problem with my Vito Sport-X van with the 3.0l v6 Om642 engine.
Running perfectly until all of a sudden at about 20% throttle lost power and went into what felt like limp mode although no CEL light came on (it has since come on after a couple of drives) Carried on until I reached my destination and plugged in my Autel OBD reader and came up with following codes;
P0299 Turbocharger/Supercharger underboost and P2463 Diesel particulate filter restriction - Soot accumulation.
So I set to work investigating, looked for boost hose leaks and saw the boost hose from turbo into intercooler and the hose from intercooler to inlet manifold were sucking inwards. This led me to thinking maybe I just have a blockage in the air filter/air inlet pipework so removed all that but it was all clear. Also removed boost pipework from turbo and the resonator. Again all clear.
The turbo vanes were free with no play.
Started the engine with all turbo compressor side pipework removed and turbo was spinning but holding my hand over the exit of the turbo there was hardly any boost coming out. I could gently blow on my hand harder!
I had my son Rev the engine and actuator arm was moving up and down a little. Also moved starting and turning off the engine. I removed the actuator and inspected the common to fail wires inside and they all look fine. Moved the arm on the turbo to check sticking vanes but this moved very easily.
Given the fault codes I thought ok the blocked DPF may be preventing the turbo spooling up properly so booked into Mercedes and had a forced regen carried out. This cleared the DPF fault but still left the issue of low boost with hoses sucking in etc and no power. They had no ideas and just said they could end up spending hours trying to narrow down the fault. They suggested turbo replacement but couldn’t explain why when vanes are free moving, actuator is working and turbo is not seized.
At a loss what to look at next??!!

kajtek1

I'd suggest to line up the things you've done in points, or events as understanding what is happening from the text can get confusing.
My first guess is that clog DPF lead to blocking exhaust flow and the flow is what runs the turbo.
Read the exhaust pressure and DPF differential pressure to start.
I know that finding qualified diesel mechanic for MB is not easy, but if you post your location, maybe someone will have recommendations.
For the future - get ScanGauge to monitor DPF when you drive.

Rawhide1205

Thanks for your reply. You’re right in long text it can get confusing.
So.......
sudden loss of power, max revs about 2800. Continuous fault not intermittent.
pulled error codes:
p0299 turbocharger underboost
p2463 DPF restriction

Carried out DPF forced regen. DPF now clear and code p2463 now gone so no exhaust flow issues.

still left with p0299 with no power.

boost hoses sucking in when revving.

turbo spinning and no play in shaft.

all air hoses, filter and turbo resonator removed. No blockages and and no boost from compressor exit even with no hoses attached

actuator moving and checked internal wires all ok

turbo variable vane arm moving very freely with actuator disconnected.

I’m in South East England.

cheers, Gary

saunders123

Hi, which Autel do you have?
Some of the Autel models has access to live data, specifically:
Exhaust back pressure.
Boost pressure.
Demanded actuator position.
If you have access to these I can try to explain what you need to look for.

If you try to clear the p0299 code does it immediately return?

Towmater

Have you checked for any blown fuses?

What does your Map sensor read when driving?

Rawhide1205

Thanks for your input

Don’t have it to hand right now but it does give some live readings although not Demanded actuator position nor I’m fairly sure exhaust back pressure. Does do boost pressure can’t remember exactly the reading but it’s pretty much 0. As I said the boost hoses collapse inward simply from the engine trying to suck air so they are obviously under negative pressure. Plus putting my hand over the turbo outlet with pipe removed it’s hardly blowing anything, despite spinning up fast. I could probably fart on my hand harder!

Yes code clears every time and comes back only after driving a few hundred yards.

with regards to exhaust back pressure I’d have thought it would still think and give code for DPF blockage or similar, and I’d at least have some boost but there is none at all? Certainly got plenty of flow out the tail pipe, and I can’t keep my hand over it at tick over, I know that’s no technical test but certainly tells me it’s not majorly blocked.

With actuator position I’d have thought I’d get some boost or possibly even over boosting but as I said there is none at all. I did try with the actuator rod disconnected manually moving the vane positions but made no difference at all in whatever position I had it.

cheers, Gary

Rawhide1205

I have checked fuses in main fuse box but not the one under drivers seat as I’m sure these are just auxiliary type stuff but will double check. I only checked main box fuses visually suppose it’s worth doing them properly with multimeter.

i did watch Maf readings whilst driving but was on my own so difficult to record what they were but I was just looking for the readings to be going up and down smoothly with throttle application. From what I’ve read I’d have different error codes and symptoms if the issue was with Maf sensor although never know with modern engines!

saunders123

So when the van is standing still and not in gear the vanes will be programmed to stay open, this will create very little "boost" this is probably why you don't feel any pressure building up.

If your 100% sure all the air intake system is free from blockages the collapsing pipe makes no sense at all, I cannot imagine the structure of the boost pipe is collapsing.
I think your going to need a more in depth diagnostic system to understand what is happening.

The exhaust back pressure before the turbo is the more important one at this point, combined with demanded actuator position and boost pressure. When the code has been cleared the live data would be very useful.

Unfortunately without some live data there isn't really anything I can help with.

Rawhide1205

Thanks I will get some live data readings tomorrow.

Yes even with all air intake and filter etc removed and turbo compressor intake just open to the air the boost hose from turbo to intercooler is collapsing completely with even slight throttle application. I get what you’re saying about being stationary in N only giving very little boost but surely not so little the hose gets sucked in? Plus as mentioned I have manually moved vane positions with actuator rod disconnected which made zero difference.

artim808

Check out this video and comments under the video:

kajtek1

If you have vacuum in intercooler hose to the level of collapsing hoses- you have to have inlet restriction.
Try to run it with "moose" clean air hose disconnected from filters.

Rawhide1205

nope 100% no blockage in intake pipes or air filter etc. As said I have run engine with these removed but quite clear to see nothing is blocking them.

Rawhide1205

Ok so the scanner is an Autel Maxidiag Elite.
what it can do on this model of Merc is not as extensive as on my old Ml for some reason. It doesn’t list this model in its directory but can still read/clear codes etc.

So some readings I have got just stationary are:

MAP- 730rpm: 96Kpa,
2000rpm: 93Kpa,
2650rpm: 57Kpa

MAF- 730rpm: 18g/s
2000rpm: 40g/s
2650rpm: 38g/s

Frp- 730rpm 30000Kpa
2000rpm 55000Kpa
2650rpm 66000Kpa

dont think any other readings it gives me are worthy of mentioning. 2650rpm is the max the engine would reach. It feels more like that’s all it can give with air restriction rather than a forced limit by the ecu.

Towmater

My guess is your turbo is toast or your intake flaps motor has shorted and is causing the no boost condition. You can check the later by pulling the Y pipe and unplugging the motor using a 4.7k ohm resistor to simulate a good motor. If your problem remains, then i would say you have to replace the turbo.

Rawhide1205

Yeah I’m starting to think it can only be the turbo just can’t get my head around how when I can see it spins up, isn’t seized, doesn’t leak oil or smoke etc!

I did think of the intake flap motor but sorta disregarded it as had that on my old ML320 which I fixed with the resistor idea. But on that I had different symptoms and fault code which pointed straight to it. Wouldn’t hurt to try I guess for the cost of a cheap resistor!

thanks for your input

Gary

kajtek1

Well.. law of physics says something has to create the vacuum you describe. Open pipes might have some restrictions, but open is open.