Fouling plugs, black smoke
#1
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Fouling plugs, black smoke
1999 Cherokee, 4.0, 195k miles
It sat for a "while". Replaced oil, oil filter, air filter, plugs, wires, cap, button and coil. Cleaned IAC and throttle body. After two tanks with sea foam still blows black when accelerating. Good power, does not run rough or misfires. Just no fuel economy and smokes.
Any ideas?
It sat for a "while". Replaced oil, oil filter, air filter, plugs, wires, cap, button and coil. Cleaned IAC and throttle body. After two tanks with sea foam still blows black when accelerating. Good power, does not run rough or misfires. Just no fuel economy and smokes.
Any ideas?
#2
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Use a scanner (OBD2) to observe the fuel trim levels. It is probably running rich, perhaps due to an O2 sensor that is providing bad values, or some other condition.
Check engine light on?
Check engine light on?
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Yes the check engine light is on. My friend checked it and it was the fuel return line error. No O2 sensor faults.
I forgot to mention that prior it running rich my Grandson sprayed the engine with simple green and then hosed it off. Could water have shorted out or damaged an electrical component?
I forgot to mention that prior it running rich my Grandson sprayed the engine with simple green and then hosed it off. Could water have shorted out or damaged an electrical component?
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Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
Jordan96xj is a master pro at deciphering the fuel trim level readings. If you get him some specific values he can help you analyze what's going on and help pin-point what the problem is.
Typically the electronics are pretty resistant to simply being hosed off, but anything is possible. You could still have a bad O2 sensor that's just not triggering a code. I would seriously put a scanner on it and get some actual data and follow Jordan's advice.
Typically the electronics are pretty resistant to simply being hosed off, but anything is possible. You could still have a bad O2 sensor that's just not triggering a code. I would seriously put a scanner on it and get some actual data and follow Jordan's advice.
#6
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Jordan96xj is a master pro at deciphering the fuel trim level readings. If you get him some specific values he can help you analyze what's going on and help pin-point what the problem is.
Typically the electronics are pretty resistant to simply being hosed off, but anything is possible. You could still have a bad O2 sensor that's just not triggering a code. I would seriously put a scanner on it and get some actual data and follow Jordan's advice.
Typically the electronics are pretty resistant to simply being hosed off, but anything is possible. You could still have a bad O2 sensor that's just not triggering a code. I would seriously put a scanner on it and get some actual data and follow Jordan's advice.
And yes, it is common for the O2 sensor to be failing in such a way where it does not cause a code for itself. Usually the code will be for running lean or rich (PO17X) type code. Unless the the sensor has lost connectivity, or its heater circuit, which sometimes will throw a distinct code just for the sensor.
Last edited by jordan96xj; 12-30-2017 at 02:48 PM.
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