94 3.4 and i have black sut like stuff coming out of the ex pipes.. any ideas why/what this could be causing this.. Car is still strong pulls/runs..

 

Carbon deposits build up in the exhaust,when you start the car the warm air condenses as it hits the cold creating moisture.

This moisture combines with the carbon to make your "black stuff".

 

um well not really the moisture comes out in a white steam type form. alot of carbon or "black stuff" is usually a sign of a rich running engine meaning your geting to much fuel to your air ratio wich could be a lot of stuff mabe time for a tune up or bad o2 sensor or even bad mass air flow sensor more likly though just needs a tune up if your service engine soon light on probly bad o2 sensor

 

Well I just changed both of the o2sensors and as far as a tune up its been done-- new plugs,wires, all of the sensors on the car are new, map,cam,crank, etc.. I really dont drive the car maybe once or twice a month.. but like I said in the begining the car pulls and runs strong.. I new 1 of my o2 sens was bad because i scaned it so I just went ahead and changed both.. the black sut still comes out but not as much..

 

Also im getting 14/7 mixture when I scan like where suppose 2, so im at a lost right now..

 

oohh take it out and drive it a little on the hard side and to clean out the system it might be just a prolong build up of carbon in the cat and on the walls of the pipes if you just changed the o2 and not drivin it much that might be all it is . by the way you seem to know your stuff im shocked you called it black stuff lol

 

Well, being that you don't run the car often, it doesn't get too much exercise to keep things in shape, in a sense.

Like when my mom sold her v6 91 RS...it ran fine after a while, but it would stumble just a bit initially, because she had this 98 Chevy 3-door to take the attention from a car that was about to be sold.

Anyway, soot (carbon) is a byproduct of combustion. You can't do anything about that even if the car is running fine, which you looking at it say it is.

Then again, you say you changed the O2 because the scanner said so....I almost want to say you didn't really diagnose what came up on the scanner. It's not like you'd be the first to change an O2 sensor just because the code had "oxygen sensor" somewhere in the definition. Probably a waste of money you will need now, but a lesson learned nonetheless.

So, I take that back, find us the code number you got from the scan and we may indeed have to tell you your car does have something wrong with it.

My guess now (just a guess without the code number you got) is that you have something like a fuel pressure regulator leaking extra fuel into the engine and the unburned fuel is what's coming out the tailpipe. The code you probably got was that the engine was running rich....that would cause that problem.

So, now you need to bust out a fuel pressure gauge and go from there, with proper diagnosis.

www.2carpros.com/topics/blksmok.htm

Use this above page link as an example of what I am getting at. A LOT of changing parts without PROPER diagnosis....

Good luck.

 

Your car is old so it has a lot of exhaust sut. Not much you can do about it other than clean it unless it's there from your car not running properly.

 

There is no MAF on an F Body 3.4L,its speed density.

 

my appolagy your right it does not have a maf on it. i was just thinkin in general and not to the specific car and i should have been more clear

 

The code was-- Left o2 sensor malfunction.. So I changed both..

 

I checked out that link.. Good stuff, but most of the solutions ive pretty much have done.. the cat convert is 2yrs old but I havent even driven 1000miles in that 2 years. fuel pump changed 2 months ago. and pressure is fine. now the regulator and cpu are the only things left. my guess would be the cpu.

 

ttt