Technical Tarry deposits in inlet manifold

[gmarshall5000]

On my jtd diesel, I have an vacuum operated egr valve. I took it off to check its operation and cleanliness. It was a bit charcoal covered but nothing to worry about - dry deposits. I checked its operation by sucking on the vacuum pipe and it seems to click open as it should. My concern was that where it goes into the inlet manifold, next to the air inlet, there was a fair quantity of sticky tar like deposit. I cleaned it as best I could.
The reason for doing all this was poor power levels throughout the rev range. I can barely reach 75mph! Any hills and its almost get out and push! I also only get 35mpg (I'm expecting more like 45mpg)
I've looked at the maf sensor, its finely coated in a thin layer of charcoal. I will try and disconnect it to see what effect that has. After that, maybe I'd suspect a split turbo hose, but even at low revs there's insignificant power.
Any ideas anyone?

 

[momoe]

Tarry deposit is par for the course, the engine breather also feeds into the inlet manifold which doesn't help.

MAF should be clean, there shouldn't be anything like charcoal on it as the MAF should be immediately downstream of the airfilter? Has the car been run without an airfilter at some point?
There are plenty of threads on cleaning MAF's , done properly it can improve matters confirming that the MAF is the issue but this tends to be transient and the long term solution is generally a new (Bosch) MAF.

Just a thought, but given you've got 'charcoal deposits' on the MAF, I'd consider cleaning the intercooler, if this was restricted in any way this would account for low power and high fuel consumption.

Worth checking error codes as these can provide useful pointers, check the hoses for splits especially the small vacuum tube from the turbo to the boost actuator.

 

[gmarshall5000]

Thanks for the advice, I've been reading several posts on other diesel engine probs and they all seem the same - to suffer from tar in inlet manifold.
Where is the intercooler? I presume its in the direction of away from the engine, following the big rubber hose that feeds air to the inlet manifold...
Only had the car 6 months, but it seems to have been regularly serviced by a Fiat garage...
I couldn't get the wires of the maf sensor. There appears to be some kind of locking tab on the connector which I haven't sussed yet

 

[gmarshall5000]

Engine transplant? Feels like I've had one! I just disconnected the MAF sensor and easily got up to (oops sorry officer) speeds in much shorter distance than I have previously thought possible. question now is why do I need a MAF sensor at all? I've read plenty posts from people running without one. I'm sure there's a good reason to buy one (eventually) or maybe just to carefully clean the existing one. Anyway, I'll be running without, for a tanks worth of Diesel just to see what a difference it also make to mpg.

 

[momoe]

MAF (Mass airflow sensor) measures the temperature and density (Mass) of the air, this allows the ECU to correct for optimum fuel burn.
Disconnecting the MAF causes the ECU to revert to default settings (which in your case were obviously better than your MAF was indicating, hence the improvement).

Default settings are probably 15c and 1013.2mb, so if the pressure is higher and the air is colder you'll get a leaner burn as the air is denser, if the pressure is lower and the temperature higher you'll burn rich as the air is rarefied/thinner/less dense.

See how you go as Bosch MAF's aren't cheap and it'll take a few thousand miles to break even on the outlay.

Intercooler on mine is in front the N/S wheelarch, best seen from underneath.