2013 XJ 5.0L SC. There's always a lot of black carbon soot on the inside of my chrome exhaust finishers (tailpipes) and I have to clean them at least once a week. I drive 90% city and 10% highway and the car runs great, with no CEL or OBDII codes.

Back in the day, before FI and OBD, black exhaust tips were a sign of too rich a fuel mixture and incorrect carburetor adjustment. Am I concerned about nothing, or is my XJ running too rich?

I presume the computers set the fuel trims and since I've had no CEL the mixture is OK.

Can anyone tell me what the fuel trims specs are? I'd like to confirm them with my OBD2 reader and Torque app.

Anyone else with really black exhaust finishers?

 

I don't know what the trims are, I haven't bought a scanner yet. I can tell you since electronic fuel injection came out I haven't seen a white exhaust since.

I was told with my first one back in the eighties that black soot was normal.

 

Get an OBD tool with live data (some don't have it). Get engine hot. Park. Watch LTFTs then if they're more than about 5 rev (about 2500 is fine), let them settle and see what they are.

Each bank has LTFT, so 4 values.

Commonly soot is OK now but LTFTs will reveal all.

An ELM327 is cheap - use Search to get a feel for what it is/does.

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If interested in how a modern petrol (gas) car works see OnBoardDiagnostics.com - Engine Basics

 

Already have the ELM327 OBDII reader and the Torque app for water temperature and voltage. Just didn't know how to use it for fuel trims.

The soot is worse than the brake dust!

 

Yes I have the black soot also and I was told it's normal.
My other cars also have the same black soot.
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