Horrible gas mileage and lots of black soot in tailpipe from a 1991 jeep Cherokee, what could be the problem?
Ever since i got my 91' cherokee ive been getting really bad gas mileage, like 9 MPG when i first got it. Since then ive replaced almost everything that has to do to with improving fuel economy except for the cat and the fuel injectors. But it's still only getting 10-11 MPG.
I recently replaced my tailpipe (from muffler out to the back) and in only 3 days the inside of the pipe is covered in black soot, which lead me to believe that its running rich. I tested my MAP sensor and the readings looked fine to me but i went ahead and got a replacement just to make sure it wasnt bad and it read the same exact thing as my old MAP sensor did.
Im not really sure where to go from here, the jeep runs great and nothing is mechanically wrong with it except for the horrible mileage. It does not burn oil, well only a tiny bit but then again every car has to burn some oil. Any input on what other things would cause the black soot and the bad mileage would be appreciated.
Sound like an injector has gone south, and is pumping fuel into the engine.
If you don't want to replace them, some quick oil change places can clean them, and they'll find any bad ones..
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