B180 cdi low end issue

[DavidHMallorca]

Hi All,

I own a 2006 B180 cdi, W245.207, manual gearbox with about 200,000kms. There is an ongoing problem where the car starts to misfire and jump at low revs from about 1,400rpms to 2,000rpms in any gear. Once it passes 2,000rpm the car accelerates normally all the way to the red line. There can also be a strong smell of diesel fumes in the cabin and I feel the fuel consumption Is not as good as it should be.

I have had it in a local garage for two weeks who say they cannot diagnose the fault and got me to come and collect the car. So far they say they have tested, the turbo, fuel injectors, EGR valve, mass air flow sensor, turbo boost pressure sensor and throttle valve. All are ok, so now they have given up. The car is now in limp home mode and will not rev beyond 3,000rpms.

This has really annoyed my as it cost me a lot of money to rent a car for the fortnight while the car was in the garage. I'm sure its not a big issue that's causing the problem and I'm hoping that one of the members here can help me or point me in the right direction.

Thanks in advance for all help/suggestions.

 

[5w155t0ny]

Does the car have a DPF?
If not, check the catalyser as it may have collapsed and is preventing throughflow on the exhaust.
(We had a Kia Sorento that had this problem many years ago with exactly the same symptoms and turned out the cat was the issue)

 

[DavidHMallorca]

I presume it has a DPF. Don't know whether it was checked or not. I have just driven the car now and the 'check engine' light is not showing on the dashboard but the car is still in limp mode and will not revs beyond 3,000pm. Stange thing is, it is driving perfectly at the low revs in every gear. Running quite nicely actually. This makes me think that the problem is electrical and is stopping the turbo kicking in.

 

[5w155t0ny]

I presume it has a DPF. Don't know whether it was checked or not. I have just driven the car now and the 'check engine' light is not showing on the dashboard but the car is still in limp mode and will not revs beyond 3,000pm. Stange thing is, it is driving perfectly at the low revs in every gear. Running quite nicely actually. This makes me think that the problem is electrical and is stopping the turbo kicking in.

Could be all manner of things. Diesel pump timing, wastegate pipe blown off, fuel filter blocked etc. Sounds more like fuel starvation than electrical tbh.
Please note, I'm not a mechanic but have been in the car trade for over 40 years and encountered pretty much every issue you can think of.
I would look into if the DPF needs to go through a regeneration process. You may be able to do it yourself if its not too far gone by driving on the motorway in 3rd gear at around 70 mph for around 10 miles to get it into regen mode to burn off the crap.

 

[DavidHMallorca]

New EGR valve fitted 6 months ago, and new oil filter fitted about four months ago, air filter ok. The strange thing now is that the car is running quite nicely now, the jumping/hesitation at low revs is gone but its still in limp home mode.

 

[ajlsl600]

Get codes read and check out historic I f main issue has gone. I think it's likely more one issue, perhaps one bringing on the second.

 

[DavidHMallorca]

Very strange. Drove the car again late this afternoon and no warning lights in dashboard, car revved like before but the jumping was back again and revving limited to about 3,000rpm max. Don't want to have to go to main dealers without a clear idea of what the problem could be as costs very high hear in Mallorca and garages inclined to rip you off.

 

[Steve@Avantgarde]

If you could get some fault codes we might be able to help you further.

Does sound like an injector fault. How did the other garage test them? They are a nightmare to remove on the old W245s. If they haven't been removed and tested then they haven't been tested properly. You'll need at least a leak off test done.

 

[DavidHMallorca]

To be honest with you, I think they were a bunch of monkeys so not sure how and if they were really tested. Would a faulty injector not work properly between 1,500rpm and 2,000rpm, then go on to rev properly? Maybe relatively poor fuel economy might indicate the injectors not working correctly. I'm not a mechanic but do have some knowledge but want to get the problem resolved without having to revert to main dealers and their prices.

 

[Steve@Avantgarde]

It could do, the lower the fuel pressure or demand, the worse it can run.

For example, if you have a worn nozzle which is dumping diesel, if the engine sings to 3-4000 rpm the quantity correction will have a bigger window in which to smooth out its running and clear the overfuel.

 

[DavidHMallorca]

I am thinking now I have three options to consider. First, sell it and get another Mercedes, second, take it to a specialist fuel injection garage, which is close by or thirdly, go to main dealer.

 

[DavidHMallorca]

Hi guys,

Just to let you know I found a local garage to me owned by a Hungarian guy who happens to be a Mercedes fan and a great mechanic. Turns out there was a number of issues with the car, some of them caused by the previous mechanic who had the car for two weeks and claimed they could not find the fault. Firstly, the mass airflow sensor was gone, secondly a feed to the turbo had been bypassed, thirdly, there were two other house around the intake system that were split or has been cut/disconnected, fourthly, there was five litres of liquid in the oil system. The mechanic thinks it's probably unburnt fuel. This was probably causing the smoking issue. The DPF was also affected. In short, the previous mechanic butchered the car. The car is now driving without smoking, without misfiring between 1,500rpm and 2,000 rpm and once the new Mac sensor is fitted tomorrow, I expect the car will be back to the way it should be.

Finally I got an answer, third time lucky. Thanks to all for the help.

 

[sonic]

Hi guys,

Just to let you know I found a local garage to me owned by a Hungarian guy who happens to be a Mercedes fan and a great mechanic. Turns out there was a number of issues with the car, some of them caused by the previous mechanic who had the car for two weeks and claimed they could not find the fault. Firstly, the mass airflow sensor was gone, secondly a feed to the turbo had been bypassed, thirdly, there were two other house around the intake system that were split or has been cut/disconnected, fourthly, there was five litres of liquid in the oil system. The mechanic thinks it's probably unburnt fuel. This was probably causing the smoking issue. The DPF was also affected. In short, the previous mechanic butchered the car. The car is now driving without smoking, without misfiring between 1,500rpm and 2,000 rpm and once the new Mac sensor is fitted tomorrow, I expect the car will be back to the way it should be.

Finally I got an answer, third time lucky. Thanks to all for the help.

A great result with your Hungarian mechanic.