Weird limp mode when towing - electrics or something else??

[Fiona/Trevor]

Hi,

Our E320 is brilliant at towing, BUT it has this annoying habit of suddenly losing power. Suddenly, acceleration is slug-like and we manage about 40mph and no more. When we stop and switch off and re-start it is normally fine again! It's rather inconvenient on the M6!
Sometimes it does it once in 6 hours, other times every half an hour. It's the only complaint we have with it as a tow car.... has anyone else experienced this?

The caravan is fairly small and light, it's only 70/75% of the car's weight.

Cheers

Fiona

 

[LostKiwi]

If sounds like it's dropping into limp mode. Have the ECU read by someone with an MB capable code reader and see what it pops up.

 

[Fiona/Trevor]

Merc going to a place with the right equipment tomorrow. Interestingly, after a year of going into limp mode when towing, it's now started doing it when it's NOT towing. Twice in 50 minutes, and under no strain at all... will update if we get an answer.

 

[Fiona/Trevor]

Right- it's been in for investigations, and there are NO fault codes showing, and the guy says the only thing he can find is a small hole in the intercooler, possibly caused by a stone chip, and it might be that.

 

[LostKiwi]

Hmmm... Dropping into limp mode but no codes?
A hole in the intercooler can cause limp mode but will usually leave a code.

 

[Wighty]

Does it only do it when towing ?

 

[Wighty]

Also was Mercedes diagnostic equipment used to look for codes ?

 

[umblecumbuz]

Has the atf level been checked recently?
A long shot - but last week I was involved in a C320 cdi with similar symptoms, and odd as it may seem, a low atf level turned out to be the culprit.

 

[Fiona/Trevor]

Does it only do it when towing ?

Started off that way (thought it was the electrics getting confused - 4 garages failed to find a problem) then a year later it's started doing it even when we aren't towing and the engine isn't even hot yet.

 

[Fiona/Trevor]

Has the atf level been checked recently?
A long shot - but last week I was involved in a C320 cdi with similar symptoms, and odd as it may seem, a low atf level turned out to be the culprit.

I shall find out!!

 

[Fiona/Trevor]

Also was Mercedes diagnostic equipment used to look for codes ?

Yes I think it was. There are never any codes popping up when it happens... we took it to Moray Firth Motors, and they are Merc specialists.

 

[Flyinspanner]

Can you fill the hole in the inter cooler with an epoxy resin/jewel dorm is a replacement required?

 

[Wheeler3108]

I've had 2 c320. Both have had the same problem with going into limp mode intermittently. The problem was the turbo actuator both times.

Car would go into limp mode and once restarted would resume as normal and not do it again for the rest of the journey.

Can be fixed with the actuator being rebuilt or replace the turbo.

Sent from my SM-G920F using Tapatalk

 

[Flyinspanner]

Jewel Dorm? Was actually JBweld when I typed it autocorrect!

 

[Fiona/Trevor]

We've found a decent secondhand intercooler for £60 so that's ok. Took it to the garage, and it broke down while it was there - they had to push it in - turning over but not starting, computer says it's fuel pump related! That's a new one to add to the list!

 

[Fiona/Trevor]

I've had 2 c320. Both have had the same problem with going into limp mode intermittently. The problem was the turbo actuator both times.

Car would go into limp mode and once restarted would resume as normal and not do it again for the rest of the journey.

Can be fixed with the actuator being rebuilt or replace the turbo.

Sent from my SM-G920F using Tapatalk

Interesting - the turbo was new BEFORE it started doing this and has again been checked recently. Don't know about the actuator.

 

[Botus]

as your specialists don't sound that special....
you could by a cheap gadget (if you have a modern smart phone) and "review live data" whilst on the move, when it plays up you'll be able to see which bit is not working. don't believe no code, more like there kit or the user is at fault

from what I read the intercooler idea was an idea, not a diagnosis


I have this and a posh adapter but never used the app on a car, as I already have better kit, I expect it can give much the same faults the merc stuff does

https://play.google.com/store/apps/details?id=de.wgsoft.scanmaster&hl=en

its needs a suitable Bluetooth adaptor or nothing happens

this needs their adaptor/dongle to make life easy

https://play.google.com/store/apps/details?id=com.iViNi.DrMercedesLite&hl=en

very posh adapter allows programming on other brands, I have bought from this guy they do a BMW bike diagnostic and coding tool, this allows programming of BMW bikes most can't do...

https://translate.google.com/translate?sl=auto&tl=en&u=https://www.obd-2.de/shop/profi-diagnose/bmw-motorrad/129/unicarscan-bt-diagnoseadapter

 

[LostKiwi]

from what I read the intercooler idea was an idea, not a diagnosis

It was just another thing to test.

Always test, don't guess.

 

[Fiona/Trevor]

Ugh, we've had the new intercooler fitted AND a fuel pump regulator (it came up saying it was faulty on the computer) and had a service, as it was due. Going like a rocket, but got limp mode again within 20 minutes.
Turbo was tested last week. That would include actuator I assume.
Can't think the Merc Specialists here don't have the right stuff to see what's going on? It never comes up with any lights on the dash when it happens. Nothing. Everything else does, but not this!
Going to look at those gadgets that tell you what's up.....

 

[bembo449]

it defo reads like the turbo actuator is failing , my 221 needed one a couple of years ago doing the very same thing but I have MB2 so could locate the problem easily , you still haven't confirmed just what these garages are using for diagnostics pal ??