Hi Scotty, I have a 2010 Chevrolet Captiva with a diesel engine, automatic transmission and 200.000 km, recently I noticed that I have a problem with black smoke and soot deposits on the car bumper, so when I start the car and let it idling I can't see any black smoke from the tailpipe, after starting to drive and accelerate the engine I get a significant amount of black smoke from the tailpipe, releasing the gas pedal it's return to normal, after driving a while I notice soot and smoke particles (that are not greasy/oily) on the back bumper of the car.
I tried to investigate the problem and made the following maintenance work: changed the air, fuel and oil filter, also changed the oil (checked the oil dipstick regularly in the past and present to see if the car burns oil, but that is not the case), also changed the DPF filter.
After that I checked the car using a Thinkcar 1S scan tool, changed the MAF sensor because I noticed that always showed a value between 14 and 15 g/s when the car was only idling, so I bought a brand new OEM MAF sensor, but the values from the new MAF sensor are almost the same as the old one showed, between 12 - 15 g/s at idling (I'm not sure if the values should be so high at idling), also I changed the EGR valve with a new one because it was tripping a P0490 error code, the valve was stuck closed.
After all this repairs and maintenances work got no other error codes so far, but the problem regarding the black smoke and the soot that is stiking on the back bumper is the same without any improvements.
I would appreciate any advice in resolving this annoying problem, thank you.