W164 turbo boost issues

[Lee Pitcher]

Hi All.

Have a 2006 ML320 that has a turbo boost issue. The story so far........

The car suddenly over night stopped boosting. Could get to 70mph but very slowly. Filled up with fuel after a week of this (was on the way for a diagnostic ironically) and instantly the problem disappeared. Normal turbo resumed. (likely pure coincidence)

One week later - back to no turbo boost. Had a test done on it with a very expensive snap on system at a garage that showed both MAF sensors had failed. I find it strange that BOTH would fail at the same time. Anyway, cleaned the MAF sensors just in case however I suspected the actuator had failed (common issue on these). Sent it away and was told there were numerous errors with it so had it refurbished. Did the resistor by pass on the swirl flap motor and fitted the new actuator however the problem still persists.

I've disconnected the MAF sensors which I assumed would give a default reading and drive normally however this hasn't helped either.

Anyone experienced the same symptoms ? The turbo does have a fair amount of soot around it

Thanks in advance for any guidance

 

[Uncle Benz]

Have you checked the fuses in the underbonnet fuse box?

 

[Lee Pitcher]

Have you checked the fuses in the underbonnet fuse box?

Must confess I haven't - which fuses should be looked at Uncle B?

 

[Uncle Benz]

I can’t remember the number, but one fuse in there supplies the operating voltage to the turbo positioner, the egr valve, MAF sensors, the swirl flap motor and the exhaust back pressure sensor. Most often its the egr or the swirl flap motor that acts up. Eventually the fuse blows and then You get fault codes for all the items that are fed by it. Easy to pull the fuses out one at a time and hold them up to the light

 

[Lee Pitcher]

I can’t remember the number, but one fuse in there supplies the operating voltage to the turbo positioner, the egr valve, MAF sensors, the swirl flap motor and the exhaust back pressure sensor. Most often its the egr or the swirl flap motor that acts up. Eventually the fuse blows and then You get fault codes for all the items that are fed by it. Easy to pull the fuses out one at a time and hold them up to the light

Cool. Cheers. Will take a look tomorrow as it's getting quite dark now. Appreciate the help though

 

[Lee Pitcher]

I can’t remember the number, but one fuse in there supplies the operating voltage to the turbo positioner, the egr valve, MAF sensors, the swirl flap motor and the exhaust back pressure sensor. Most often its the egr or the swirl flap motor that acts up. Eventually the fuse blows and then You get fault codes for all the items that are fed by it. Easy to pull the fuses out one at a time and hold them up to the light

Couldn't wait until tomorrow so with torchlight found fuse 104 (15amp) has blown. The report on my turbo actuator said it was drawing 3 times the amount of power it should so I'm hopeful this is the case and swapping the fuse over will resolve the issues. Fingers crossed hey. Will find out tomorrow

 

[Uncle Benz]

If it blows again its a case of unplugging items one at a time until you find the culprit. I start at the egr. It sounds like you’ve done a resistor mod on the swirl flap motor, so that one’s already accounted for

 

[Uncle Benz]

The suspense is killing me!

 

[Lee Pitcher]

The suspense is killing me!

Haha ! Morning Uncle B. Sorted it late yesterday afternoon but been a bit busy to post. Fuse 104 replaced and all works ok now thank goodness.

All the years in the motor industry and didn't even think of checking for a fuse which is quite a schoolboy error !

When the actuator was sent away and tested they did say it was drawing 3 times the power it should so realistically should have expected that it would have blown something. I just expected it all to work again !

Thanks for the guidance on that fuse. You're a star.Really appreciated. I'd have still been swearing !

Best regards

 

[bembo449]

you will find when ever this fault occurs , that fuse must be looked at after the repair is done as the symptom will remain til a new fuse is fitted