I have a 1997 Sonata 2.0 A/T..the problem I'm having is I noticed that the car is leaving black soot on the back of the car,like its getting too much fuel,does not run rough,I've pulled the plugs,they do have alot of carbon on them,the check engine light was on,had it checked,it was the O2 sensor in ther manifold,replaced it,still noticed the black soot on the car good for about 6 mos. check engine light came back on...this time I replaced both O2 sensors check engine light off..still getting the black soot on the car,not as much but its there, by the tailpipe and back bumper(car is white)...I dont know what to do...are there any TSB's on this any suggestions would be helpful...the gas mileage is probably suffering also..I want to fix the problem..not just throw parts at it.
Vince

 

Take the car to a competent shop and have a complete tune-up done on the vehicle.
Good Luck,
Brant

 

There are different things that can cause black smoke out the tailpipe. A bad diaphram in a fuel pressure regulator can suck raw fuel directly into the intake. Pull the hose off , see if it's wet or pinch the hose off & see if it works better. Coolant temp sensor can make them run rich also. A bad mass air flow sensor, Camshaft timing, etc. See if you can have someone hook up a scan tool and look at Injector duration, long and short term fuel trim. It can be more expensive to just start throwing parts on , than having someone hook up to it and try to pinpoint the problem.