C Class Loss of Power issue

[RoDDDimuS]

I have a 2005 Mercedes C Class CDI220 Avangarde with 70k on the clock

Problem:
On the motorway car enters limp home and will not rev beyond 3000 or kick down, once it enters this 0-40mph seems fine but above 40 there is little power.

Restarting the car removes the issue.

The issue also doesnt seem to happen if the car is kept below 50mph.

Codes: When the issue occurs the fault code is P0299 Turbo/Super Charger Underboost

Any ideas on a fix? i havent had chance to inspect the Hoses connected to the turbo yet im guessing this is the best place to start?

any help appreciated

 

[BlackC55]

http://www.mbclub.co.uk/forums/engine/144927-lack-power-cdi-what-do.html

 

[BlackC55]

Check the top boost hose first.

 

[RoDDDimuS]

ok will do, is there anything in particular im looking for other than a loose fit/holes/cracks?

thanks

 

[BlackC55]

Just a crack in the top section.

 

[RoDDDimuS]

I had a look at the top hose there didn't seem to be any holes or cracks but couldn't see it fully. This is my first merc, what would you suggest removing to make the inspection easier?

Also I don't know if these points are related but it seems to be ok when its cold for say the first 10mins running from cold no matter what speed.

It also seems to give an inconsistent temperature from the engine, is this a merc quirk? for example sometimes the car runs slightly over 80 on the gauge others like when I came into work today it was running at 60ish the whole way

 

[RoDDDimuS]

Also am going to be damaging anything further by running the car while it has this fault?

 

[BlackC55]

No

 

[RoDDDimuS]

I checked the hoses and couldnt see any obvious holes or cracks.

I decided while i had the it off to clean the MAF with electrical contact cleaner, i didnt actually remove the sensor i squirted it all down the housing etc.

When i started the car back up the gear changes were slightly irractic, and when i pulled on the motorway to go for a test run the car rev'd to nearly 5000rpm and engine management light came on but it seemed to return to normal and when into the standard limp home mode. I got it back checked the code still p0299 cleared it and started back up and it seemed much better, i took it on the motorway and tried it and where as usually it would go into limp almost straight away it didnt for a good while, it did eventually on the return journey but it had definitely extended the period of time before the fault happened

Is there anything to take from that or am i clutching at straws thinking that it points to a MAF sensor fault? is it worth changing the MAF or should just take it in and get it properly fixed by an expert?

 

[savinda92]

If you have an engine light indication in the cluster try diagnosing the car using xentry. Then the you can identify the faults. If it is current try erasing the faults and test run the vehicle. What are the fault codes you get??

 

[RoDDDimuS]

This is the one and only time i have gotten an engine management light on the dash all the other times the car enters limp mode after a couple of miles on the motorway without any warning lights or notification.

The light came on in the first run after cleaning the MAF while i was on the slip road and put my foot down the car seemed to get stuck in second revving up to nearly 5000 until i backed out the throttle - auto box is in C too so it wasnt just trying to be sporty, after i restart the light didnt come back.

the only error code i get of the OBD is the P0299 underboost error

 

[savinda92]

Did u try erasing the fault memory and test the vehicle?

 

[RoDDDimuS]

Ive cleared the code on a few occasions it comes back after the limp home mode fault comes on.

The weird thing is if I stay below 50mph there is no problem I can drive for as long as I want without the fault coming on. Also even after it has 0-40mph seems relatively ok but then the power just disappears

Like I said after I cleaned the MAF I got a very long (comparably) run without a problem its now back to normal so basically within 1-3miles on the motorway it will happen.

its hard to know exactly when because there is no obvious sign until you put your foot down and there is nothing there

 

[E270 Owner]

Get it on MB Star and complete the Charge Pressure and turbo test function.

 

[RoDDDimuS]

Ok hooked it up to the proper diagnostic loads of old codes in there so cleared the lot and took the car for a run.

Interesting side note it was slightly rough running the revs seemed to sway back and forth ever so slightly, its been rougher since i cleaned the MAF i feel

ok so got back and hooked it up to the machine and got 1 fault code which was the following:

CDI 3 - Common Rail Diesel Injection 3
code 2359-001 Check engine air system Too low boost pressure.

So from the machine it tells me 2 possible causes DPF or leak in the system - how does this sound to the experts out there.

 

[E270 Owner]

ok

1. Charge pressure system leak
2. Stuck VNT turbo vanes
3. Faulty turbo actuator
4. MAP sensor (least likely)

I have all of those cause this fault code in the past.

 

[RoDDDimuS]

ok

1. Charge pressure system leak
2. Stuck VNT turbo vanes
3. Faulty turbo actuator
4. MAP sensor (least likely)

I have all of those cause this fault code in the past.

Any ideas how i could narrow that down from here, or am just going to have to take it in somewhere?.

I am still getting inconsistent temp readings from the engine also. Some journeys its 80-85 and others like today it seemed stuck at 60 for most the journey sometimes its bob on 80

is this normal could it be part of the fault or a different fault.

 

[RoDDDimuS]

Any ideas how i could narrow that down from here, or am just going to have to take it in somewhere?.

I am still getting inconsistent temp readings from the engine also. Some journeys its 80-85 and others like today it seemed stuck at 60 for most the journey sometimes its bob on 80

is this normal could it be part of the fault or a different fault.

I got an engine warning light again on the way home hooked it up to the DAS and still same error but this time with an engine warning light?

Can anyone explain why cleaning the MAF or at least through the housing (i didnt actually remove the sensor) would cause this fault to worsen? i have had 2 engine management lights since i did that and the car is now running rougher than it was before i did that. I use Electronic Contact Cleaner as was recommended but the car seems to be running worse as a result.

Is it worth changing the MAF and seeing if it fixes the issue or am i kidding myself that it will be that simple?

my logic being if the MAF was working fine then "cleaning" it wouldnt effect anything to do with the fault, but it definitely has changed since then

 

[E270 Owner]

Any ideas how i could narrow that down from here, or am just going to have to take it in somewhere?.

I am still getting inconsistent temp readings from the engine also. Some journeys its 80-85 and others like today it seemed stuck at 60 for most the journey sometimes its bob on 80

is this normal could it be part of the fault or a different fault.

Common fault with the thermostat/housing, replace it with a genuine MB one for quality purposes.

I got an engine warning light again on the way home hooked it up to the DAS and still same error but this time with an engine warning light?

Can anyone explain why cleaning the MAF or at least through the housing (i didnt actually remove the sensor) would cause this fault to worsen? i have had 2 engine management lights since i did that and the car is now running rougher than it was before i did that. I use Electronic Contact Cleaner as was recommended but the car seems to be running worse as a result.

Is it worth changing the MAF and seeing if it fixes the issue or am i kidding myself that it will be that simple?

my logic being if the MAF was working fine then "cleaning" it wouldnt effect anything to do with the fault, but it definitely has changed since then

A faulty MAF is a faulty MAF cleaning them can cause more problems if its already faulty......

 

[RoDDDimuS]

So would you give that a whirl - its £160 for a Genuine Bosch one which im willing to take a punt on as i got the car cheap, unless folk think there is no chance this will fix it, but i know the MAF can cause the fault im having from what ive read