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1999 Dodge Grand Caravan

Question: carbon deposit in tail pipe

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schamb, 3.3L V6, Alexandria, VA, June 13, 2011, 13:28
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 Rookie

I noticed carbon black deposit film in tail pipe that has never been there before. Had new plugs and wires put on ~25K miles ago, and engine runs fine with no noticable smoke or unburned gas smell in the exhaust. Asked a mechanic today when I brought the car in to have a dripping leak in the fuel filter/gas line fixed and he wanted to replace the coolant temperature sensor because incorrect coolant temperature data to the engine computer can result in incorrect fuel mixture to the engine. This sounds reasonable, but are there other potential causes I should consider rather than the "replace everything that could cause the problem" approach? Thanks.

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  • Answer #1

    DaveJHM June 13, 2011, 22:51
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    Did the mechanic have evidence of an improper coolant temperature being recorded and sent? In theory, the coolant temperature sensor is important to setting proper fuel, spark and air mixtures. If the engine is running too cool, or the sensor thinks so, indeed - you could have more fuel go through your engine and eventually get into your exhaust...as you are describing, having black deposits.

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