Steve Rothwell answering your ENGINE MANAGEMENT queries
FORD S-MAX
Q My friend has a 2010 Ford S-MAX 2.0 diesel bought a couple of years ago. When he first got the vehicle, it had a loud turbo whistle which I quickly Identified as a bad intercooler (it had a hole in it). Now fixed.
Now on occasions it seems to bog down when under hard acceleration and then when he changes down a big puff of black smoke is emitted, then off it goes again all fine. Once whilst on holiday it left him stranded as wouldn’t gain any power, wouldn’t even rev properly at standstill.
I have looked at the entire intake system from filter to turbo then to intercooler and inlet manifold, etc., the only fault I found was where the air pipe attaches to the turbo the two bolts were NOT tight and there was a little oil around the area. However, it did improve the problem for a while.
My question is – is the turbo seal perished and would that cause this issue. It’s a nightmare to do as one bolt is hidden and getting a tool on it is a pain but if I need to do it I will.
A The black smoke is normally an indication of a mixture imbalance, and this could be due to a number of factors. The lack of power or bogging down at the same time does sound as though they are connected to the problem. The two main areas that should be checked are the MAF sensor and the EGR valve.
Starting with the MAF sensor this may have become contaminated from the earlier issue with the intercooler failure, and it could be the case that oil has worked its way around the induction system and ended up coating the hot wire sensor. This will prevent the MAF sensor from reading correctly and could give the symptoms your friend has on their S-MAX.
Cleaning the sensor using an isopropyl alcohol or dedicated MAF cleaning spray may help with the issue. It is important to not make contact with the hot wire sensor with anything other than the cleaning fluid, and to ensure that the cleaning fluid has completely dried before refitting the unit and starting the engine.
If this does not help in remedying the issue, then it may be that the EGR valve is not responding quickly enough and upsetting the air induction during the acceleration. Again, this may be remedied by cleaning using a suitable cleaner.
As you have not mentioned the presence of an engine management light, then I would presume that no codes are present, but if the EML has appeared, then it would be good to get the codes read as this may assist with the location of the problem.
The black smoke may also be due to an injector issue, and if after carrying out the previous actions no resolution is found, then a leak-off test on the injectors may help to identify a dribbling or faulty injector that may be contributing to the problem. As this is black smoke then it wou
