06 HHR has had many problems, currently spews Heavy black smoke taking off from stops, fuel economy went from 7.0 L per 100 km to 8.8 L per 100 km, rear of car covered in black soot. Recent history had eng lite on many times, cleared, driven and retested, changed all sensors that repeated on tester tool; first was intake cam sensor, then intake cam sensor near cam gear, then knock sensor, rear O2 and front O2..this has all happened last few months, eng oil gets gas washed and gets new oil/filter changes frequently (dont want blow-by)...
Car has been to GM dealer and GM trained diagnostic tech at NAPA shop, no faults found at any shop...

"Still smokin" I should call this car the Cheech/Chong mobile

Does anybody had same issues ??

I am a retired auto tech and this is really buggin me...flooding carb I can fix !!

 

which engine, supercharged or n/a?

The newer 2.4cylinder engines with direct injection have been leaking fuel past the injection pumps. Think yours is to old to have those options.



What was done so far?
Fuel pressure high?
regulator diaphram ruptured?
What is the fuel trim at during launch, idleing, cruise and wot?
what codes are set?
any aftermarket air filters, intakes, exhaust or ecm tunes ?