ML 270 limp mode

[kebo57]

Evening all
Would the said below be classed as limp mode
Motor won't rev over 2200 rpm
Accelerates slowly in every gear up to 2200 rpm
Max speed 80 mph on flat
Max speed up hill, speed drops of depending on gradient
No kick down
Motor will rev over 2200 rpm if I drop a gear manually
Could anyone help please
What could be the problem
Kevin

 

[BlackC55]

Air mass
Inlet port shutt off motor/flaps stuck shut
Leaky intercooler
Faulty EGR
Vacuum transducer faulty

 

[BlackC55]

You need the fault memory read really. Get that done first.

Hope this helps

 

[Andy Wr]

Mine did exactly the same last month once only, the only other thing that has happened a few times including 5 mins ago is the alarm going off on the drive, wonder if the battery is on its way out and causing a voltage drop, is that possible?

 

[kebo57]

Air mass
Inlet port shutt off motor/flaps stuck shut
Leaky intercooler
Faulty EGR
Vacuum transducer faulty

Nice one BlackC55 thanks for the reply

Air mass Ive swaped the maf no change

Inlet port shutt off motor, I checked this and the rail was not moving when engine was running sort of locked up. when engine was off i could move servomotor then came back to life but no change

Leaky intercooler I think there is some weeping

Faulty EGR previous to cleaning this Ive had fault codes read but didn't show egr fault

Vacuum transducer faulty Where would I locate this Item

 

[kebo57]

Mine did exactly the same last month once only, the only other thing that has happened a few times including 5 mins ago is the alarm going off on the drive, wonder if the battery is on its way out and causing a voltage drop, is that possible?

Hi Andy do you mean the drive out side your home
Kevin

 

[Andy Wr]

Hi Andy do you mean the drive out side your home
Kevin

Yes, it has now happened 6 or 7 times in the last 2 months, getting a bit annoyed now and the neighbors love me.

 

[kebo57]

Yes, it has now happened 6 or 7 times in the last 2 months, getting a bit annoyed now and the neighbors love me.

Ive never had this happen to me I can check voltage of battary engine on and off for you tomorrow
Kevin

 

[BlackC55]

Nice one BlackC55 thanks for the reply

Air mass Ive swaped the maf no change

Inlet port shutt off motor, I checked this and the rail was not moving when engine was running sort of locked up. when engine was off i could move servomotor then came back to life but no change

Leaky intercooler I think there is some weeping

Faulty EGR previous to cleaning this Ive had fault codes read but didn't show egr fault

Vacuum transducer faulty Where would I locate this Item

Its on the left hand side as you open the bonnet. Trace the vacuum pipe from the turbo actuator to it. It a small black plastic device that has an electrical connector as well as vacuum connections.

 

[kebo57]

Its on the left hand side as you open the bonnet. Trace the vacuum pipe from the turbo actuator to it. It a small black plastic device that has an electrical connector as well as vacuum connections.

Is there one of these on the other side next to the throtal potenshiomiter

PS your diagnosis was bob on I have a staliing problem for some 20 weeks over 70 mph light acceleration turnes in to a juddering revs drop for split second you could probably sort it buy your 300 miles away
Kevin

 

[BlackC55]

Is there one of these on the other side next to the throtal potenshiomiter

PS your diagnosis was bob on I have a staliing problem for some 20 weeks over 70 mph light acceleration turnes in to a juddering revs drop for split second you could probably sort it buy your 300 miles away
Kevin

How did you know I was a specialist??????

And the answer to your question ...yes

 

[kebo57]

How did you know I was a specialist??????
And the answer to your question ...yes

Sorry I've let the cat out the bag
Biography:
Mercedes Independent specialist
Location:
South coast
Interests:
Cars, cars, Cosworths
Occupation:
Owner of Specialist garage
How would i tests the vacuum transducer
could I swap these around
kevin
ps I'm logging of now I must sort 814 for the test,throttle potentiometer "whow that spell was miles off"

 

[BlackC55]

I am not to sure that you can test it. But you can see if there is a vacuum there on the output side to the turbo actuator???

 

[kebo57]

I am not to sure that you can test it. But you can see if there is a vacuum there on the output side to the turbo actuator???

Ive swapped them round and it seems to be accelerating OK, but when stationary the flap rail isn't opening when stationary. the one on the offside front seems to be grumbling

the rail is trying to move but only 20 thow are so like it not getting the correct signal
I'm going to swap them back to duplicate the problem
Kevin
PS thanks for your help I not going to admit I'm brow beat with this motor

 

[BlackC55]

Flap rail????

Do you mean the inlet port shut off under the inlet manifold.?

 

[kebo57]

Do you mean the inlet port shut off under the inlet manifold.?

Yes thats what I meant whilst I got your attention I must recap
I swapped the vacum potentiometers round and it went back to limp mode for wont of a better word, (inlet port shut off not operating)
So I have swapped them back to the original way and went for a blast on Mway
Everything is OK inlet port shut off is operating (don,t no if operation is correctly)
The two Vacuum transducer I swapped some time ago but they never gave me any trouble until now
Would this be pointing to a new Vacuum transducer but how would I no which one has a fault

I still have the stall over 70 mph revs drop 200 revs then come back with sort of misfire feels like vibration on the flat, up hill more of a sort of stall misfire Its hard to describe
I have cleaned the inlet manifold, Inlet port shut off flaps, egr valve
I could send some pic's of the Item's
would the said symptoms relate to the egr valve our the Inlet port shutt off servo motor
Sorry if the thread is hard to follow
Kevin

 

[BlackC55]

I'm confused....

 

[psmart]

Do you mean the inlet port shut off under the inlet manifold.?

Yes thats what I meant whilst I got your attention I must recap
I swapped the vacum potentiometers round and it went back to limp mode for wont of a better word, (inlet port shut off not operating)
So I have swapped them back to the original way and went for a blast on Mway
Everything is OK inlet port shut off is operating (don,t no if operation is correctly)
The two Vacuum transducer I swapped some time ago but they never gave me any trouble until now
Would this be pointing to a new Vacuum transducer but how would I no which one has a fault

I still have the stall over 70 mph revs drop 200 revs then come back with sort of misfire feels like vibration on the flat, up hill more of a sort of stall misfire Its hard to describe
I have cleaned the inlet manifold, Inlet port shut off flaps, egr valve
I could send some pic's of the Item's
would the said symptoms relate to the egr valve our the Inlet port shutt off servo motor
Sorry if the thread is hard to follow
Kevin

Ill just chip in if I may. The two transducers Boost Pressure Control and EGR have different part numbers, so as a guess, the vacuum to voltage level will be different. If the ECU sends x milli-amps (I just remembered, these are current controlled, not voltage) to the BPCVT expecting the Turbo to give y psi boost and it gives y-2 psi boost, it will associate it with a fault and go into limp home mode. This is what could be happening when you swap the two transducers around.

Are the air filters at the bottom of the transducers clean? If there not sensing atmospheric pressure correctly, this could give a problem.

Change the BPCVT transducer and see if the stall still occurs. Check the vacuum pressure (I posted it somewhere on a thread last year when I replaced my turbo) and check that the turbo actuator arm doesnt stick.

Also, there are some known problems with the Turbo/actuator vanes leading to Mercedes replacing them, so it might even be down this track (just a guess, but last resort).

 

[Blobcat]

Change the BPCVT transducer and see if the stall still occurs. Check the vacuum pressure (I posted it somewhere on a thread last year when I replaced my turbo) and check that the turbo actuator arm doesnt stick.

Also, there are some known problems with the Turbo/actuator vanes leading to Mercedes replacing them, so it might even be down this track (just a guess, but last resort).

Here is your boost pressure thread - http://forums.mercedesclub.org.uk/showthread.php?t=17603

 

[kebo57]

Thanks for the replays BlackC55 and Blobcat
I will read the associated thread from blobcat till it all sinks in

Please dint give up on me yet BlackC55
Ive had the stall for 20 weeks but I swapped vacum potentiometers around some 6 week ago but only now as it gone to limp
I shouldn't of done this they are back in there correct places now

Blobcat the air filters at the bottom of the transducers
I've sucked on these there seem to be slight restriction, but both filters a equal could i remove filter for test
I will Change the BPCVT transducer and see if the stall still occurs
Kevin