Black Tailpipe/ lotsa Carbon?

91Woody

NAXJA Forum User

Location

Manchester, NH

• Mar 14, 2008

• #1

I thought I recalled reading somewhere that this was a sign of a bad o2 sensor. I also get pretty crappy mileage, but that could be caused by a lot of other things. I replaced the exhaust about two weeks ago and have no CEL, but the tailpipe is already pitch black and has the black exterior ring forming nicely now.
Can anyone confirm or deny the o2 sensor possibility. My multimeter has a dead battery, so checking the voltage is out right now. I have 171K miles on a '91 4.0 HO, so it may be original, it may not.
Thanks

 

crystalship1

NAXJA Forum User

Location

Indianapolis, IN.

• Mar 14, 2008

• #2

Sounds like it's running rich. An O2 sensor could very well be the culprit.

Good Luck!! :cheers:

 

G

Glacialbass

NAXJA Forum User

Location

Morrison, CO

• Mar 14, 2008

• #3

O2 sensor is a pretty quick/cheap fix for that. throw a battery in the multi-meter, test it, and replace it

I just replaced mine and it certainly cut down on the carbon build up in the exhaust.

 

91Woody

NAXJA Forum User

Location

Manchester, NH

• Mar 14, 2008

• #4

Thanks for the replies, I'll be checking into it further.

 

X

xjbubba

NAXJA Member # 1524

Location

santa barbara, ca

• Mar 14, 2008

• #5

If the O2 sensor is original, at 170K/miles, it's time to change it!
O2 sensors get "lazy", resulting in richer mixture.

 

D

dizzymac

NAXJA Forum User

Location

New Hampshire

• Mar 14, 2008

• #6

Check the MAP too, if voltage is off it can run rich.

 

91Woody

NAXJA Forum User

Location

Manchester, NH

• Mar 14, 2008

• #7

thanks, will do o2 sensor and check MAP sensor. I hope the o2 sensor isn't original, but I have had so many other issues to deal with since I got it last year that if it wasn't throwing a code, I wasn't changing it. I haven't had such good luck with my XJ, but at least I'm running out of things to go wrong on it

 

90Blue_XJ

NAXJA Forum User

Location

In yer postz fixin yer spellinz.

• Mar 14, 2008

• #8

Another vote for O2 sensor.

 

91Woody

NAXJA Forum User

Location

Manchester, NH

• Mar 17, 2008

• #9

I'm changing o2 sensor out today. Tomorrow i have another 100 mile trip to go on, so perhaps I'll save a half gallon of fuel
If anything noticeable happens I'll post up.