ml270 cdi Loss of Power

tony jr

Senior Member
Joined
May 5, 2009
Messages
581
Reaction score
10
Location
Nottingham
Your Mercedes
GL320 X164 2007
Hi

Can someone please help me ? My ml 270 cdi 2003 has just started to loose power (sound familiar!) – but not all of the time. When you drive off in the morning the car works fine if you put your foot down you can feel the car accelerate and hear the turbo kick in with the engine revving past 4000 rpm. However, after about 20 min when the car has warmed up it suddenly looses power feeling very sluggish not revving beyond 2500 rpm even with your foot to the floor (almost like limp home mode but without any warning light). This makes it slow to go uphill or overtaking when you need the power.

I have been looking at similar problems that people have reported and come to the conclusion that it might be a faulty MAF sensor or possibly the fuel filter. I have tried unplugging the MAF sensor but this does not appear to make any difference.

Can someone please advise if I’m on the right track and should I try cleaning the MAF sensor with isopropanol or just replace it? If this fails what should I do next?

Any advice would be very much-appreciated

Thanks
 

Cole@MBS

Forum Supporter
Authorised Forum Supporter
Joined
Dec 1, 2008
Messages
13,702
Reaction score
950
Age
54
Location
Southampton
Website
www.mbssouthampton.co.uk
Your Mercedes
124 300 CE 24 Coupe, C220CDI, Porsche 911 4s, Dolomite sprint,
Could be anything from airmass sensor to blocked Cat to a inlet port shut off motor!!

needs a short test really!!
 
OP
T

tony jr

Senior Member
Joined
May 5, 2009
Messages
581
Reaction score
10
Location
Nottingham
Your Mercedes
GL320 X164 2007
  • Thread Starter
  • Thread starter
  • #3
If the CAT was blocked would you not expect power loss all the time and not intermittent
 

Cole@MBS

Forum Supporter
Authorised Forum Supporter
Joined
Dec 1, 2008
Messages
13,702
Reaction score
950
Age
54
Location
Southampton
Website
www.mbssouthampton.co.uk
Your Mercedes
124 300 CE 24 Coupe, C220CDI, Porsche 911 4s, Dolomite sprint,
it would be worse when hotter then cold, but just gave you a few pointers!!
 

johnyb

New Member
Joined
Jul 6, 2009
Messages
2
Reaction score
0
I was experiencing the exact same problems with my ML270. After getting hooked up to the Star Diog and Mercedes it came up with a fault in the Inlet Port Shut Off. What I have found so far is that the rod connecting the Servo Motor and long shaft that the flaps attach to wich make them open and close was missing and must have broken off.

Does anyone know if I should be able to move that long rod wich is attached to the inlet port flaps? I figured I should be able to open and close them by moving with my hand back and forward. If it does not move does that mean one or more could be jamed?

Cheers,
 

kebo57

Senior Member
Joined
Oct 4, 2006
Messages
894
Reaction score
3
Location
Lanc's
Your Mercedes
ml270
I was experiencing the exact same problems with my ML270. After getting hooked up to the Star Diog and Mercedes it came up with a fault in the Inlet Port Shut Off. What I have found so far is that the rod connecting the Servo Motor and long shaft that the flaps attach to wich make them open and close was missing and must have broken off.

Does anyone know if I should be able to move that long rod wich is attached to the inlet port flaps? I figured I should be able to open and close them by moving with my hand back and forward. If it does not move does that mean one or more could be jamed?

Cheers,
Hi yes you are correct, that link could still be there but only connected at one end & rotated round in line with the long rail so might look like its is missing

Kevin
 

ruane

Active Member
Joined
May 1, 2009
Messages
37
Reaction score
0
My 270cdi had a problem with very similar symptoms. Started off fine, then after a few miles it seemed like the turbo stopped working. Boot to the floor, but no signifigant response, very very slugish to accelerate of climb, and topped out around 75mph. Stopping the car, turning off, and restarting it would temporarily clear the prob, only for it toi reoccur after 10 or 15 mins. Few days later a hissing noise developed, and was related to acceleration, and turbo pressure. Assumed I'd blown a pipe off - no big deal like.

Brought it to a local indie, who diagnosed it as a blocked cat. Repaired that day and 5000miles later haven't had a problem.
 
OP
T

tony jr

Senior Member
Joined
May 5, 2009
Messages
581
Reaction score
10
Location
Nottingham
Your Mercedes
GL320 X164 2007
  • Thread Starter
  • Thread starter
  • #8
blocked cat sounds expensive - any idea of cost?
 
OP
T

tony jr

Senior Member
Joined
May 5, 2009
Messages
581
Reaction score
10
Location
Nottingham
Your Mercedes
GL320 X164 2007
  • Thread Starter
  • Thread starter
  • #9
update

Update:

After crawling home last night I decided to try cleaning the MAF sensor. I removed the MAF sensor (Pierburg A6110940048) from it’s housing and soaked the end of it in isopropyl alcohol for a few minutes (this released some dirty oily grime from the sensor) then sprayed the sensor with electrical contract cleaner, before replacing back in the car. I then took the car for a quick test drive around the block. The result was amazing the car felt like new the acceleration was much better than I can remember.

This morning I took the car on a 30 mile trip the power, acceleration, turbo performance was great to start with then after about 25 miles the power dropped off feeling sluggish not revving beyond 2500 rpm again.

Any ideas what to try next? Do you think the MAF is faulty and needs a more thorough clean or replacing? Or do you think that the MAF is nothing to do with the problem? Could it be the CAT? How would I tell? Could anyone explain to me if it is the cat why the problem is not there all of the time and why it does not effect the tick over (when the cat blocked on my E-class the engine would stall at tick over)? Someone suggested changing the fuel filter and or fuel pre-filters – where are the pre-filters?

Thanks for all your help so far
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
You could unplug the MAF and try the car,,they seldom clean up, and on a diesel the air flow is much greater than on a petrol.

I would say that a replacement will fix it. JiB on the forum sells then at around £60
 
OP
T

tony jr

Senior Member
Joined
May 5, 2009
Messages
581
Reaction score
10
Location
Nottingham
Your Mercedes
GL320 X164 2007
  • Thread Starter
  • Thread starter
  • #11
You could unplug the MAF and try the car,,they seldom clean up, and on a diesel the air flow is much greater than on a petrol.

I would say that a replacement will fix it. JiB on the forum sells then at around £60

Hi

When I unplugged the MAF it did not appear to make any difference at all - still limited revs. Would you have expected this to have solved the problem or does the ml "fail safe" and go into limp mode when the sensor fails or you unplug it? Does this affect your recomendation to replace the MAF?
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
Reaction score
367
Age
89
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
The unplugging does not always work, it would be cheaper to replace the MAF than to have the car checked on STAR,,,

I cannot just tell someone to go and buy some thing, its a hard call
 
OP
T

tony jr

Senior Member
Joined
May 5, 2009
Messages
581
Reaction score
10
Location
Nottingham
Your Mercedes
GL320 X164 2007
  • Thread Starter
  • Thread starter
  • #13
update

Just picked up a new MAF sensor from my local MB dealer (£51 + VAT - good price). Will fit tonight and let you know how I get on. I will also change the fuel filter just in case. Does anyone know if the ml has a pre-filter or just the main filter (with a built in prefilter).

thanks
 

Alex Crow

Senior Member
Joined
Jul 9, 2009
Messages
10,677
Reaction score
47
Location
Super Suffolk
Your Mercedes
W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
it`s just the main filter. also check you air filter. other likely causes are sticking egr valve, shot/sticking manifold flaps, blocked cat/s, split intercooler or hose or wastegate vacuum modulator.
 
OP
T

tony jr

Senior Member
Joined
May 5, 2009
Messages
581
Reaction score
10
Location
Nottingham
Your Mercedes
GL320 X164 2007
  • Thread Starter
  • Thread starter
  • #15
problem solved

I have just replaced the mass air flow sensor then taken the car on a 6 mile test drive. What a difference the new sensor made - never had so much power! Who would have thought a small sensor would make such a difference!

A very big thanks to everyone who offered useful advise.
 

Rourkester

New Member
Joined
Dec 30, 2009
Messages
5
Reaction score
0
I have the same model (ML270cdi) and have had the same problem. I changed the MAF sensor which seemed to cure the problem but it has now reoccured after 2 weeks. I had a lot of exhaust gasses from the back box so assumed the cat was ok but now can not get it to rev past 3000. I am suspecting a blocked cat.
 

norraban

New Member
Joined
Oct 6, 2010
Messages
2
Reaction score
0
Location
Brisbane
Your Mercedes
ML 270 CDI 2001
Hi,
Am experiencing the same intermittent loss of power with my ML270 CDI as "Tony jr" as it becomes dangerous to drive on the highway especially where a hill is concerned or when overtaking. The car will not exceed 40kph on some hills. Switching off and restarting temporarily fixes the problem. MAF sensor has been replaced, but did not fix problem. According to my mechanic, the problem is caused by a lack of boost pressure, but the cause of this could be a variety of things including a faulty or blocked Cat converter.
It is not a requirement of Australian design rules to retain the Cat converter, so will the car run properly without the Cat converter in place. ie replace the Cat converter with a matching piece of exhaust tubing ??
Norraban
 

oigle

Senior Member
Joined
Mar 15, 2005
Messages
3,467
Reaction score
914
Age
83
Location
Redcliffe, Queensland, Australia
Website
members.optusnet.com.au
Your Mercedes
2003 ML270 sold but not forgotten. 2022 Kia EV6 RWD LR
Hi,
Am experiencing the same intermittent loss of power with my ML270 CDI as "Tony jr" as it becomes dangerous to drive on the highway especially where a hill is concerned or when overtaking. The car will not exceed 40kph on some hills. Switching off and restarting temporarily fixes the problem. MAF sensor has been replaced, but did not fix problem. According to my mechanic, the problem is caused by a lack of boost pressure, but the cause of this could be a variety of things including a faulty or blocked Cat converter.
It is not a requirement of Australian design rules to retain the Cat converter, so will the car run properly without the Cat converter in place. ie replace the Cat converter with a matching piece of exhaust tubing ??
Norraban

Even though it isn't mandatory for diesels to have a cat here, if the vehicle is fitted with one, it must be retained.
Of course, this is just the law. Sugest that you remove the guts of the cat but leave the original "box" there for visual recognition.
The car will run quite perfectly without a cat. Little bit noisier.
Sounds like you should get the motor on star for a diagnosis before spending any more money. You could be getting a problem with your egr valve sticking - this causes limp mode. There are a couple of big threads on the egr problems and a way of taking them out of the system. Worth a read.
 

norraban

New Member
Joined
Oct 6, 2010
Messages
2
Reaction score
0
Location
Brisbane
Your Mercedes
ML 270 CDI 2001
Thanks Oigle,
Will suggest this to the service agent before they remove the Cat.
 

AIB understand your special Mercedes deserves a special insurance policy. We have a refreshing attitude to insuring high performance, modified, imported or classic and vintage cars and deal with the UK’s leading insurers. We offer discounts for length of ownership, where the vehicle is kept overnight and limiting the mileage and can also cater for those clients who need higher mileage and business use. To obtain a quotation please call the team on 02380 268351 or visit us atAIB Insurance
Top Bottom