ML270 Speed Lockdown

[psmart]

I've just returned from MBenzNL (great company and people, well recommended family concern) and as Ileft Holland (70mph limit) into Germany, I opened up my ML to get away from some annoying slow drivers.

Touched 120mph on the gauge for about 10 minutes (I know theirs a lot of people in this forum who hate speed, sorry, but I agree with the Germans on this one ), when suddenly the car started to decelerate to 85mph. I kicked down, nothing doing, I manually selected 4th, nothing doing, it just stayed at 85mph. I braked to 60, hit kickdown and it gradually increased to 85mph!

Remembering about Limp Home Mode, I pulled in to the nearest Gas Station, switched off, switched on and everything was back to normal, 120mph! I kept my speed to 90/100mph the rest of the way home.

Could this be a German Limp Home Mode?

 

[television]

Who knows, if it does it again, its something to think about, there should have been light on dash if a real problem.


Malcolm

 

[jberks]

Agreed. Wait for it to happen again. Then chances are you'll need a new MAS. I agree with Malcolm about the light, except that I didn't get one either. I think the bulb may have gone! Does your check-engine light work?

 

[psmart]

Thanks guys, I'm driving her down to Zell Am See this weekend (1 week holiday) so will see if she mis-behaves.

I gave it some serious thought at the weekend, and things I forgot to mention:
1) I used the new Super Diesel (V-Power) for the first time. I wanted to see if it gave any extra power/economy on the 250mile round trip on Saturday.
2) It could be related to the slow acceleration I mentioned in an earlier post when it came back from Mercedes (glow plug change). I also didnt use contact cleaner on the connections, just re-seated them. Up until it went to Mercedes, Id never had any bother.
3) The Turbo doesnt make that sweet wolfwhistle noise, more of a slight wheeze. Still accelerates very well and will hit 120mph (on a 115mph car).
4) Steve (MBenzNL) did some re-wiring for me, so it is possible a wire was disturbed.

MAS sensor, do you have a part number? Steve (MBenzNL) advised that parts are cheaper here in Germany, so whilst Im here, I might as well buy any part that will need replacing on a 5.5 year old ML.

In terms of lights, all the dash lights are working.

 

[timhammond]

Hi, My ML 270 (4 year old) is suffering what sounds like the same problem with speed lockdown. Has anyone identified the solution? eg do we need to have the Air Mass sensor changed?
We did have a blowing injector previously and had that rectified but the glow light warning light still shows occasionally.
Any help will be much appreciated before I take it in to Mercedes for an expensive diagnosis

thanks
Tim

 

[jberks]

if an off-on solves it then very possibly. But you really need the fault codes.

 

[psmart]

Just completed 600miles and no problems, but I changed back to standard diesel, so either Ive got a minor electrical fault, or the Diesel Ultimate/V-Power is not compatible with my car. As food for thought, I got 22mpg on Diesel Ultimate/V-power, I got 27mpg on the 600mile run on standard Diesel.
When the fault occurred, it seemed like the engine was limiting power, perhaps the V-power diesel was causing an overheat, it would freely rev to 4500rpm, but when engaged to the gearbox, seemed to have the torque restricted, hence getting to 85mph, but slowly. Its not the same as Ive read from other members where the car electronically restricted the speed to 30mph.
Tim, if the problem keeps recurring, forget Merc, lookup an independent Merc authorised specialist (in London or Leeds, you have Merc Care), it will be cheaper and they will be more interested in doing a good job. Also, get your glow plug issue sorted (read my other post), as it may cost you.

 

[davebox]

take a look at this post. Seems that a few are having problems like this. sligh diff's with when it happens but same overall problem. LIMP MODE.
http://forums.mercedesclub.org.uk/showthread.php?t=16612
Im just waiting for the next time (if there is one). If it happens again, I'll drive it to my local dealer and not let them switch it off untill they have driven it. I'm sure they think I'm dreaming the problem. :wink: would non mind if it had done any real miliage, 9k 18months old when I bought it. it's now 2 years old with 11.8k and this problem has shown its head four times. Stealer has told me its sorted so I'm going on one of those possitive thinking trips. I'll let you all know how it pans out in a couple of months.
DB

 

[psmart]

Thanks, interesting thread, sounds very much like what I experienced, both at speed and when I got the car back from Merc. Will wait until it occurs again, hopefully never!
Our C220Cdi needed an air mass sensor after I was foolish enough to get it hand-car-washed. Apparently the sensor is in the door (???) and the high power pressure wash they use killed it. The symptoms for this were 30mph restricted with the failure noted in the console-dash.

 

[psmart]

The ML now has 58K on the clock (from 56K when the problem last occurred) and I have had no relapse, despite journeys in varied conditions. The Turbo has returned to its sweet wolfwhistle and the car pulled 125mph today en-route to Munich (for a brief time, I dont like to thrash her!).

A friend of mine, chief engineer Leeds University (retired after 30 years), points to most of the problems being related to bad connectors and has quoted me numerous examples. A tip from him is that most of the problems we are seeing could be related to oxidised connectors (nb. if you pull out a connector, the oxide on the end of the male pin will wipe onto the female, thus creating a bad connection next time you plug the connector in, also connectors can be oxidised before Merc assemble them, leaving a bad connection waiting to happen). As per another post, where Rajinder was having numerous CAN problems, the best way to sort out connectors is to scrape the male pins with a knife, then use contact cleaner (high grade) then re-insert them. The serated male pins will scour the female and make a very good connection.

So, if you've got the patience, pull off all connectors on the air intake methodically and perform the above.

 

[psmart]

Solution to Lockdown

Problem solved.... at least for a MY2001 ML.

The diagnostic code for this problem is1470

This is the code relating to a Boost pressure control vacuum transducer and the symptoms are that the ECU turns off the Turbo and the engine becomes normally aspirated, hence slow acceleration and slow top speed.

The Boost pressure control vacuum transducer is located in the front left of the engine compartment, just in front of the black semi-ball unit, has 2 pipes going into it and at the base, has what looks like a fuel filter, but is actually the atmospheric pressure sensor input.

On my car, bad contacts where to blame. Disconnecing the unit whilst the engine was running switches the engine into the normally aspirated mode described above.

If anyone needs more detailed information on this, please message me.

 

[psmart]

Follow up summary

No answers on my earlier thread about a Turbo related noise, so I'll summarise what has happened to see if anyone recognises the situation. I will update this thread as more information/resolution is found, ideal for all 270 diesel owners.

Summary:
1. ML returned from Merc after glow plug replacement, vehicle refused to accelerate. Turbo whistle was not present, more like a muted wheeze.
2. After disconnecting and reconnecting all air related sensors and connectors around engine top, acceleration returned, turbo whistle returned.
3. ML went to MBenzNL to have UHI and Bi-Xenon fitted. On return journey, ML locked down to 85mph or 3000rpm on load in any gear. Stop/start cured the problem. Weather was sleet and snow.
4. More time spent on re-seating connectors, no re-occurence of problem.
5. ML was tuned to 210bhp via re-map and covered more than 800 miles without problem.
6. Diagnostic reader purchased, fault code read-out was P1470, fault with Boost pressure transducer.
7. Transducer checked, looked ok and fault P1470 could be made to re-occur by disconnecting it, so contacts cleaned.
8. Heavy rain on a 150 mile journey, and a new symptom started. At around 2-3000rpm, if accelerator was at 1/3 to 1/2 throttle, a noise could be heard like an amplified cricket, a high pitched shrill, just as though compressed air was being blown through rubber. No power loss or other symptoms seen. At 1/4 throttle, turbo whistle can be heard and everything normal. At full throttle, everything normal, no power loss etc.
9. Checked for noise location and it came from within the surrounds of the Air Filter, but without a smoke-pellet test, wont be able to verify if it is leaking compressed air.
10. Re-flashed original ECU map back into ML, problem still exists. Will keep original ECU map until problem is resolved.

I have read numerous threads about air-intake problems (ie. fractured inter-cooler) but none seem to apply, but I will progress through checks in an orderly fashion. Unfortunately, its a 3 hour (works time) trip for me to get the car to a dealer and back and I dont have a garage, so resolution will be time staking. The car is due back in the UK next month, so if I havent resolved it, will let Merc-Care take a look.

 

[psmart]

A further update to this thread, after studying several resources:

The car experienced 2 surges approx 2-3 months ago, where the car went into un-controlled acceleration, despite foot being off the Accelerator. I put this down to possible dirt in the Accelerator cable. It could still be the case (dirt in the Accelerator cable), but after studying several other information resources (whose information is not available on this forum, unless the Search indexing is out-of-date), there exists the strong case that it is linked to this lockdown scenario. Apparently, a leak internal to the Turbo charger could see the engine oil being sucked out and blown into the combustion chambers, spinning up the Turbo faster etc. I saw no leaks on my inspection, and the air-filter was clean, but as this is a condition which could be fatal, if you come across a similar situation, I recommend you take the action Im just taking, disabling the Boost Pressure Transducer, forcing error P1470 so that the Turbo will not spin up. The car still runs fine, just quick acceleration is gone, and a top speed of 85mph.

 

[Blobcat]

One of the subcontractors we use had an ML270 on an X Plate. The car suffered from poor running and the vehicle was very sluggish. Main dealer took the injectors out to check them. What they didn't say is that they had crossed one of the threads in the head. The dealer had another garage heli-coil an injector back in. This worked for awhile until driving on the M4 they noticed a puff of smoke from under the bonnet and no power. Pulled onto the hard shoulder and just had time to get out of the car before it went up in flames. Amazing what diesel at 1600bar can do.
They gave them a new E-class for 8 months before they sorted it all out.

 

[psmart]

Almost there with the solution...

To further this thread, please read my earlier post: http://forums.mercedesclub.org.uk/showthread.php?t=9776&page=2 and I strongly advise that should your Glow Plug light come on after ignition, to get them replaced, immediately! Why, read-on:

Before returning the ML from the Alps to Düsseldorf, we spent some time analysing what the problem was, and we found it!

First, the basics:
o The Turbo sits directly on the Exhaust manifold and interconnects via a rigid triangular manifold. The Primary Catalytic converter attaches to the Turbo exhaust outlet via a movable seal, to allow for engine movement/vibrations etc.
o The Turbo Charger is activated by a vacuum, sucking on an actuator, the higher the vacuum, the more engaged the Turbo Vanes become, and the more boost pressure is applied to the intake manifold/cylinders.
o The Vacuum is generated by the Vacuum Pump and regulated by The Boost Pressure Transducer, which is a needle valve type device, the higher the current you pump into it, the more vacuum it allows to go through to the Turbo. In order to avoid 'lock-up', the Transducer is vented to Atmospheric air, and the Atmospheric air intake has an air-filter to prevent damage.

The Analysis:
o Without stripping it down, we cant say for 100%, but it looks like the Turbo to Primary Catalytic Converter seal has gone, otherwise a crack has developed on the Primary Catalytic converter or the Turbo housing AT THE SEAL.
o The joint is covered in soot, but no burning of surrounding components has taken place, primarily due to the exhaust shielding, which is also densely covered in soot. The seal, when the turbo is on-load, has a minute leak, generating the shrill insect like noise, which masks the re-assuring Turbo wolfwhistle and was pumping out soot and additional heat into the engine bay.
o As there was extra heat and soot in the engine bay on heavy load, the Boost Pressure Transducer air-filter would become clogged and also the vacuum would not be constant (our assumption) due to heat, thus the ECU would detect a fault (P1470) and shutdown Boost Pressure Transducer actuation, thereby disabling the Turbo.

Why the link to Glow Plugs?
o When the Glow Plug light started to come on after ignition, I assumed it was indicating that it was switching on the Glow Plugs for longer, as it was sub-zero temperatures.
o When the temperatures really dropped, below -20'c, starting the engine was a major headache, and it is then when I discovered that the Glow Plug light indicates Glow Plug failure.
o I still needed to use the car, so I cranked the car until it started, switching on/off numerous times to heat what glowplugs worked up! The engine backfired several times, and black sooty smoke came out of what I thought was the air-inlet! It wasnt, it was from the joint mentioned above!!!

Once I have the car back in the UK in a few weeks, I'll start the strip down and decide wether I want to attempt the job, or let Merc-Care fix it.

Just on the + side, if you disconnect the Turbo Boost Transducer and drive at a steady 60-70mph, you get 39.44125 mpg with a car loaded with 1 driver and about 1/2 tonne of equipment (making for a 3 tonne car), driving up and down motorways which are worse than the M62 Pennine route! If you need to save dosh, this could be an idea worth considering, pulling the connector off the Boost Pressure Transducer!!!

 

[WILCO]

Hi Folks

Have got a high mileage c270cdi auto, had it from new and seem to be having a similar problem to yours. A new exhaust has now been fitted but to no avail. I am down on fuel consumption from 41 to 35 and when i accelerate from 85 to 95 i lose power and the accelerator becomes virtually useless.
The last time this happened i pulled over into the services, went for a jimmy and the power returned. My garage has plugged the diagnostic box of tricks in and comes up with the 1470 fault code. Any help would be much appreciated. Thanks

 

[pjherd]

Hi Everyone,

I have a ML320 Petrol and LPG conversion. After long run approx 200 miles, or short run 10 miles, 3 cylinders shut down and car goes into limp mode. Problem remedied when ignition turned off then on again, the restart sorts it all out and after short time it happens again. Can anyone shed any light on this?. Thanks

 

[supermed41]

The ML now has 58K on the clock (from 56K when the problem last occurred) and I have had no relapse, despite journeys in varied conditions. The Turbo has returned to its sweet wolfwhistle and the car pulled 125mph today en-route to Munich (for a brief time, I dont like to thrash her!).

A friend of mine, chief engineer Leeds University (retired after 30 years), points to most of the problems being related to bad connectors and has quoted me numerous examples. A tip from him is that most of the problems we are seeing could be related to oxidised connectors (nb. if you pull out a connector, the oxide on the end of the male pin will wipe onto the female, thus creating a bad connection next time you plug the connector in, also connectors can be oxidised before Merc assemble them, leaving a bad connection waiting to happen). As per another post, where Rajinder was having numerous CAN problems, the best way to sort out connectors is to scrape the male pins with a knife, then use contact cleaner (high grade) then re-insert them. The serated male pins will scour the female and make a very good connection.

So, if you've got the patience, pull off all connectors on the air intake methodically and perform the above.

psmart, where can i buy high grade contact cleaner, and can you give me a name for contact cleaner product please.

 

[dieselman]

psmart, where can i buy high grade contact cleaner, and can you give me a name for contact cleaner product please.

Maplin sell contact cleaner.

 

[dieselman]

The Analysis:
o Without stripping it down, we cant say for 100%, but it looks like the Turbo to Primary Catalytic Converter seal has gone, otherwise a crack has developed on the Primary Catalytic converter or the Turbo housing AT THE SEAL.
o The joint is covered in soot, but no burning of surrounding components has taken place, primarily due to the exhaust shielding, which is also densely covered in soot. The seal, when the turbo is on-load, has a minute leak, generating the shrill insect like noise, which masks the re-assuring Turbo wolfwhistle and was pumping out soot and additional heat into the engine bay.

Your cat is blocked.