W639 loss of power

[luke2152]

Hello. I'm having an unusual issue with my 111 vito. Put simply, when I start it cold it has no power. Literally just makes 50mph at a push. But it drives perfectly. No warning lights, no stuttering just no power. As it warms up it doesn't improve. But if I park up for 5 minutes it usually drives fine. If I just cycle the engine on and off it usually doesn't fix things.

This issue started about two months ago and has gone gradually from a rare event to more than 50% of the time. When it runs well it runs perfectly. No fault codes are coming up. I had a few legacy ones for EGR but I removed it and cleaned it and not had that code recently.

Seems to me like a classic dirty maf. I unplugged the maf to drive it and it made no difference but didn't put a warning light on or flag up a fault code which really surprised me as I thought it would immediately notice the maf unplugged. I still think maf is likely culprit as I've seen the similar lack of power/otherwise behaving itself on other vehicles. But I'm thinking equally could be fuel pressure, temperature sensor etc. I'm somewhat confident that it is not in a limp mode but injecting minimal fuel due to some innaccurate sensor reading. I also replaced the fuel filter in case it was partially clogged and the cold temperature was causing the fuel to gel up and block it, however this wasn't the case.

Anyone experienced this before and want to chip in before I slap a new MAF on? (and anyone know what a gen one goes for?) Thanks

 

[rls]

It sounds like a similar issue to mine, It may need a new / refurbed turbo actuator.
Mine started off the same, very occasionally losing power - with no EML warning, then gradually got more common and now get the EML a lot!
It is due for a new turbo in the new year, I decided it made more sense to change the turbo that will come with a new actuator than just change the actuator, as it is not an easy job to do because of the location of the turbo and limited space in the engine bay.


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[luke2152]

Thanks for the reply. I moved the actuator by hand and it moves smoothly and can hear the gears operating. That doesn't confirm its ok because it could be the actuator motor but I would have thought that would be a permanent problem and not intermittent. In fact when it works it works well and doesn't fail (until the next day) which is not what one would expect from a failing actuator. I had the EML come up again and it was EGR range/performance (a generic code from a cheap reader). So I'm going to first try an EGR emulator (plugs in where EGR would normally, leaving EGR closed but gives MAF appropriate readings when EGR should be open to make it look like EGR is working). Cheaper than an EGR valve and should be a permanent replacement. However I'm not so sure that is the problem and not just a coincidence.

 

[luke2152]

Well I've not had any luck with EGR or MAF sensor. I've tested the turbo by removing the actuator arm and lockwiring the vnt arm in the full and off positions. Neither improve the cold performance. Hooked back up and still the same (no power when cold, no power once warmed up until the engine is switched off and on and then it runs perfectly all day). All I can think of is fuel temp and air inlet temp sensors. Any of which could fool the ecu into thinking it doesn't need to give you much fuel if they fail. Maybe fuel pressure and MAP sensors as well but I wouldn't expect them to behave differently when hot/cold.

 

[luke2152]

Well problem solved and pics attached. RLS was correct, it was indeed the actuator. I couldn't find a replacement actuator so I removed mine and opened it up. There are 7 extremely thin wires which run from the connector to the circuit board and two of them had sheared from vibration or whatever (so I guess they were expanding when hot and making contact but not when cold). I ripped all the wires out, cut out the blue insulation material and exposed the metal pads the wires attached to. The pads are coated in some unknown metal which can't be soldered so I scraped them until I'd exposed copper and then soldered new heavier copper wires in place of the originals. Quite fiddly and far from pretty but bolted back together and now it works fine!