My C250TD is lacking power!

[KLP 92]

I have a small prob with my C250.

I have a loss of power, only a slight loss, its like driving the car without the superchip that i had fitted. The car has been excellent since the superchip was fitted a few months ago, a real pleasure to drive!

Since this morning, its felt sluggish. I made a detour to GF this afternoon and placed the car on diagnostics. The only fault code was a minor one, something to do with the air pressure. I made a trip to MB stratford and picked a new MAP (manifild absolute pressure sensor). I read previously that Jimmy had similar probs and it was this unit so i changed it.

At this point i should mention that i fitted a K&N air filter day before yesterday I know it harms MAS sensors etc, BUT mine doesn't have one as after the air box the pipe goes straight intthe turbo. Maybe completely unrelated but even so when i fitted the new sensor i changed the filter back to the old one.

Any the prob is still there, its still slightly sluggish. I had presumed that maybe the superchip had gone wrong, but after a call to them they assured me as the chip was changed the car couldn't revert back to its old settings! They have offered to check it but are 100% the problem lies elsewhere. They stated that they get alot of queries like mine and 99% are faulty MAS sensors, nut mine doesn't have one!

The turbo definately kicks in, and definately doesn't feel like a pipe's come loose, as it normally blows off completely!

Any ideas as what could be wrong? I'll probably change the diesel filters next but am not entirely convinced its the prob!

 

[jimmy]

There are only 2 sensors on the C250TD, the MAP sensor and an air temperature sensor located on the return pipe from the intercooler between the radiator and air box.

I am not 100% sure if you have to have the fault codes erased or not before it will go back to normal.

The other thing to check would be the EGR valve.

 

[Parrot of Doom]

Well if you change the air filter one day, and the following day performance is affected, I'd say theres your problem tbh.

 

[KLP 92]

There are only 2 sensors on the C250TD, the MAP sensor and an air temperature sensor located on the return pipe from the intercooler between the radiator and air box.

I am not 100% sure if you have to have the fault codes erased or not before it will go back to normal.

The other thing to check would be the EGR valve.

The EGR valve was checked yesterday and was functioning ok, will reset the ecu to see if it makes a difference.

 

[jimmy]

Well if you change the air filter one day, and the following day performance is affected, I'd say theres your problem tbh.

Unlikely on this engine, I ran mine with a K&N filter for 2 years, 35K miles and had no problems. These engines do not have the fragile MAS sensors or air flow sensors like the petrol cars.

 

[KLP 92]

EGR valve checked on diagnostics and is working correctly. All fault codes erased but still the same. WIll change the diesel filters next week and put a bottle of injector cleaner in to see if it helps.

Will also check all the turbo pipes just to make sure.

 

[Dieselman]

Connect a boost gauge to the MAP sensor line. This will check the boost is there, if not check the wastegate is working. It could be the vacuum actuator or the wastegate is stuck.

If the boost is ok check for restricted exhaust.

It would be unlikely to be the fuel side but worth checking anyway, even for excess air in the system as that will cause the injection to go retarded.

 

[KLP 92]

So far i have changed the air intake temp sensor and the MAP sensor. MAde no difference to the power.

I have changed the diesel filters as well, no difference.

Plugged into diagnostics, no fault codes now the the EGR valve is function correctly. The diagnostics programme tells you when it opens/closes.

The car just feels like its holding back, it still goes but alot less than before. I find myself regularly using 1st gear, a thing that i did not do once the car was superchipped.

Any other ideas on what it could be? I don't thinks its a turbo pipe, as normally the car goes really sluggish when it comes off!

 

[Will]

What about Dieselman's turbo diagnostics? Sounds like a worth line of investigation

Good Luck,

Will

 

[KLP 92]

What about Dieselman's turbo diagnostics? Sounds like a worth line of investigation

Good Luck,

Will

Can't do it myself so will have it looked at tomorrow morning! The car still drives fines so it hasn't been at the top of the priority list as alot of time has been going into diagnosing a misfire on the 560.

 

[Dieselman]

I hate to say this but what about either melted turbo tips or blocked catalyst.

 

[KLP 92]

I hate to say this but what about either melted turbo tips or blocked catalyst.

The cats been checked, no prob there.

Wouldn't melted turbo tips give me more than a 10-20% power loss? My turbo has been a bit whiny, but its been like that since i bought it, over a year ago.

 

[230K]

Hi

Have you checked for any bubbles in your fuel lines around the filter housing when she is running. Park her nose up on a hill overnight an see if you have any probs starting. Just a thought.

230K

 

[mstar01]

i am not sure i also have a c250 td sport manual, i am a new td owner i am a bit dissapointed with the performance i was just wondering is there any routine checks i should do? its just had a b service.

 

[KLP 92]

i am not sure i also have a c250 td sport manual, i am a new td owner i am a bit dissapointed with the performance i was just wondering is there any routine checks i should do? its just had a b service.

Check the air filter, fuel filters etc. Otherwise superchip and remove the cat for noticcable power gains.

I believe my lack of power was due to a partially blocked CAT.

 

[mstar01]

is there any signs (visually etc) that the cat is not working 100%?

 

[Dieselman]

MAybe more black smoke as the engine has to work harder but nothing really obvious unless it's really blocked.
The proper test is to screw a pressure guage into the exhaust upstream of the cat.