Power Loss On C250td Estate

[ponterob]

Power loss. black oily gunge in turbo charger air ducts and bottom of the inlet manifold. Starting to change filters but can't find the fuel pre-filter. Supposed to be to the left of the fuel pump, but not that I can see! Any thoughts from folks, please?
Cheers
Ponterob

 

[wireman]

clean your MAF

 

[ponterob]

Thanks for reply - what does MAF stand for, I have various thoughts! (I've read the thread on cleaning the MAF, wiser by far, but no nearer to knowing the terminology!) Any idea why oil would accumulate in the air ducts and inlet manifold? Is it a problem or an inconvenience. Do you know where the pre-filter is?
Cheers
Rob

 

[wireman]

The MAF is a small device in the inlet airflow to measure the quantity of air ingested by the engine, it is used on diesels to determine the maximum amout of fuel that can be delivered into the engine without causing too much black smoke. It works by having a small computer controled heating element which is cooled by the passing airflow, the amount of electric power used to maintain the temperature giving a measure of the mass of air being drawn into the engine. from this value the maximum quantity (to remain "green") of fuel can be computed.
When it is not functioning correctly the engine control unit, (yet another computer) goes into "I dont know whats happening mode" which limits the fuel delivery to a quantity that is not very likely to cause black smoke and reduces the avalable torque range of the engine.

You need a MAF in the system especialy when the engine has a turbo since such an engine will take different amounts of air depending on the turbo speed (which will rise relatively slowly) and available boost pressure which will take a short time to reach equilibrium (turbo lag).

Perhaps others with immediate experience of your model will provide you with more pointers to the problem.


I have inadvertently destroyed a MAF (whilst attempting to clean it) from a rover 25, it is a similar type (from bosch) as the merc units and uses a small 0.5 x 2mm window over silicon slab as its sensing element hidden inside a plastic moulded box which sits in the airflow, The Rover forums have lots of similar questions to yours so it would seem that this is a common fault with many cars, If the MAF is heavily contaminated (mine was) it may not be possible to clean it properly and replacement is required.
The Maf lives in a plastic hose about 3" dia and 5" long, it is secured into this by a pair of torx bolts on an oval plate, you need to remove the MAF from the plastic hose to clean it, see the DIY section. If you need to replace it try and buy the bit on the oval plate from bosch, quote the 10 digit number next to the Bosch trademark.
The plasic hose is car specific to fit your engine and it costs £147 for the complete rover unit at Euro parts, I have been told since that the sensor part is only £60 that means I paid £87 for a piece of unwanted plastic.

On my older 250D the pre filter is a double ended plastic thing inline with the fuel pipe between the steel bit that comes from the tank and the fuel lift pump which is low down on the LH side of my engine.

Oil accumulates in the intake both from the engine crancase breather system and as a result of condensation of the tiny amount of hot oil which escapes from the turbocharger, a small/tiny amount is normal but if the amount of oil gets excessive (i.e. dripping when you stop, or getting filthy quickly after cleaning out) the turbo seals are probably faulty and must be attended to, failing to do this could be very expensive.

 

[KLP 92]

The C250 does NOT have a MAF sensor.

It has a MAP sensor located on the passenger side bulkhead near to the engine, it has one vacuum line connected to it. This can cause performance loss if its faulty.

Other culprits: Leaking turbo hose, EGR valve ( you can strip it down, clean and then lubricate), Turbo vacuum actuator, dirty air filter, knackered turbo etc.

I would start with the basics. Clean the EGR valve, remove inlet manifold and de-gunk it. Take it from there.

 

[KLP 92]

Power loss. black oily gunge in turbo charger air ducts and bottom of the inlet manifold. Starting to change filters but can't find the fuel pre-filter. Supposed to be to the left of the fuel pump, but not that I can see! Any thoughts from folks, please?
Cheers
Ponterob

Pre filter is located on the left of the main fuel filter. Its held in by one 10mm bolt if i remember correctly. Its like a small white mesh type cylindrical shaped object.

 

[ponterob]

Many thanks to everyone - I have learnt much. Now to put it into practise ...... !