Black smoke from tail pipe?
#1
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Join Date: Mar 2010
Location: Cambridge OH-IO
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Year: 94/00/99
Model: Cherokee
Engine: 4.0
Black smoke from tail pipe?
Another question about this 99 GC I bought. Its only getting 7-10 mpg. I changed the plugs(they were black) and changed the coolant temp sensor.(the guy at autozone said a bad one would make it run like crap) And I changed the oil/air filter. But it still blows very black smoke/oil out the tail pipe. And under the hood were the fuses are, there are relays for the O2 sensors.(places fo them to go anyway)mine are not there. And there are NO little slots for a relay to plug into either. Should there be?
ps. When is warmed up the back smoke stops for the most part.
any help is appr. thanks
ps. When is warmed up the back smoke stops for the most part.
any help is appr. thanks
#3
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Year: 94/00/99
Model: Cherokee
Engine: 4.0
It has no cat. I bought it this way but Ive had other cars that didnt have a cat and they did not do this. I know I need to try a mass air flow sensor/throttle position sensor. But I really wondered about the missing O2 sensor relays.
#5
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Year: 1988
Model: Cherokee
Engine: AMC242
Black smoke? 7-9mpg? You're running awfully rich.
If the HEGO heater relay(s) are missing, that's probably your problem. Should repalce with standard DIN relays, from what I've seen (maybe mini-DIN relays - check the sockets. A DIN relay is about a 1" cube, not including terminals - while a mini-DIN is half as wide.) No HEGO signal will cause the ECU to fail over into a very rich "limp home mode." (Not quite rich enough to cause cylinder washdown, but it can be close.)
If you've been running like this for a while, you're probably going to be in for changing your HEGO sensors as well - they'll have become clogged up with carbon.
And by all means - replace the cat! There's really no good reason to run without one, we don't need the Greenies after us any more than they already are, and the good designs (like those by, say, Random Technologies) can actually improve exhaust airflow slightly!
If the HEGO heater relay(s) are missing, that's probably your problem. Should repalce with standard DIN relays, from what I've seen (maybe mini-DIN relays - check the sockets. A DIN relay is about a 1" cube, not including terminals - while a mini-DIN is half as wide.) No HEGO signal will cause the ECU to fail over into a very rich "limp home mode." (Not quite rich enough to cause cylinder washdown, but it can be close.)
If you've been running like this for a while, you're probably going to be in for changing your HEGO sensors as well - they'll have become clogged up with carbon.
And by all means - replace the cat! There's really no good reason to run without one, we don't need the Greenies after us any more than they already are, and the good designs (like those by, say, Random Technologies) can actually improve exhaust airflow slightly!
#6
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Year: 1992
Model: Cherokee
Engine: 4.0
your running rich and I bet it has to with the 02 sensros. Off the top of my head you should have 2 (could be wrong) one before the cat and one after
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