I get black soot when I stick my finger in the tail pipe of my 1996 cherokee(4.0L). I checked the plugs and the electrodes were a nice tan color. Is the carbon in the tail pipe normal? I thought fuel injected engines ran clean enough that the tailpipe remained clean.

 

Push~ Anyone knows?

 

Great point. I wonder if it could run right 98% if the time, but still have soot from the time it's not exactly right. It's not nearly hot enough back there to burn it off. The milage #'s should tell the real story. I get above 20 highway, 16 knocking around, stock.

Actually my 90 runs pretty white, not tan. (tan/chocolate was for carbs) I think your MAP sensor is still up on the firewall? (96 is a sort of transition year....)

I just checked. My finger came out with no fresh looking soot, just a little "color/tint...
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There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will cause problems.