My 98 75TD Bravo failed the MOT at the weekend due to excessive black smoke. The car has been stood for a few months but I gave it a good drive around before the MOT and changed oil,oil filter, fuel filter etc before the MOT. The pass level is 3.0 and mine was showing 3.97 average. I have since replaced the air filter, added some stop smoke products to both the oil and fuel and also added some diesel injector cleaner and given the car another good run. The car seemed just as bad so I have pulled the hose from the crankcase breather unit that sits on top of the inlet manifold and have run a hose from the breather to vent under the car and have blanked off the hose that leads back into the air intake. The idea of this is so any fumes are now chucked out of the breather and vented under the car and I know that the car is only sucking clean air through the filter as the crankcase does seem to breathing quite heavily. I took the car today for another emissions test and it is now WORSE than it was, averaging over 5.0!! I would have expected that with all the additives in and the fact that it is now breathing clean air it would be better than it was but the opposite has happened...HELP!!! what else can I check/adjust?? the MOT tester suggested that the pump may have been adjusted to give it more power, can I adjust the pump to reduce power(and emissions) just to get it through the test???

engine is overfueling. many possible causes such as sensor failure (often MAF/MAP). any TD owners care to share their tips for reducing the black clouds?

Hello,

you may have an overfuelling problem as jug suggests. Is the engine pulling properly ?, i.e. as powerful as usual ?. Check all your hoses, esp from turbo to inlet manifold. Then check that the turbo is working properly, although when just revving the engine for testing there is no real boost produced. Have a look at the pump and make sure the cold start advance is not stuck on, and have a look for signs of tampering with the fuel metering adjustment. poor timing or a bad injector could also cause this. There is no MAF sensor on the TD75, it is mechanical injection only.

What mileage is on the engine ?

smoke treatments are probably a waste of money, usually a gallon of petrol to a full tank is used to reduce smoke before testing..

Owen.

stylers said:

There is no MAF sensor on the TD75, it is mechanical injection only.

Click to expand...

whoops

I have disconnected the cold start device in case this was faulty and have checked the pipe from inlet manifold to turbo and all is ok. One thing I did find is that the lambda sensor is loose in the downpipe even though the securing nut is very tight - would this be causing the problem?

The car had sat with a flat battery for quite a while and when I jump started it I was revving it quite hard - someone has suggested that the ecu may have reset itself as the battery was totally dead so when i jumped it and revved it the ecu may have set itself to that style of running. If i disconnect the battery for 45 minutes and then reconnect to reset the ecu again and run the engine in a more "normal" fashion will the ecu act accordingly and input less fuel??

Failing this, would adjusting the potentiometer on the throttle linkage have any affect?
Failing this, can any adjustment be made to the pump? the timing seems ok as the car starts, idles and drives well its just bloody smokey!!

There is definitely no lambda sensor on diesels, do you perhaps mean a sensor on the intake pipe ?. I'm not familiar with the TD75, but if it has an EGR system, you should also check that this is ok, if there is a vacuum pipe to the actuator you can disconnect and block it off to check, but it could still be leaking. older diesel ECU's dont learn any parameters from the engine, so resetting ECU wont do anything. Again, not totally familiar with the engine, but i suspect that the ECU may only control EGR, immobilising and heater plugs..
you could wind back the pump and see if it has any effect, but I'd recommend a diesel specialist first to see if anything else is wrong..

Owen.

Hi Stylers,

Thanks for the info. The car definately has something that looks like a lambda sensor screwed into the downpipe almost where it meets the exhaust manifold. This is then linked to the egr valve. I have finally located the bolts that will allow me to move the pump so this is my first plan of action. I'll mark the current position and hopefully move it enough to reduce the smoke but still run ok. At the end of the day if I can reduce the smoke enough to get a pass I can always put it back to how it is now after the MOT!:devil: