Old car, low miles........... some black smoke

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Old 11-19-12, 03:17 AM
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Old car, low miles........... some black smoke

I just bought a 92 Dodge Dynasty with 78,000 one owner actual miles. Bought from the original old lady who only drove the car on Sunday and to the mall or grocery store.

The car runs good, but I noticed black smoke coming out of the exhaust when I rev the motor up. Not a lot of smoke, but enough to bother me as I want to get 200,000 miles out of this car. The motor is a 3.3 V6

What should I do to this car to get it to stop smoking? I've been told if it was white/gray smoke that was a sign of worn rings, but what is black smoke a sign of?
 
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Old 11-19-12, 04:08 AM
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Black smoke is indicative of unburned gas/overly rich mixture.
 
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Old 11-19-12, 04:12 AM
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Agree. First thing to do would be the routine replacement of all tune-up items if that hasn't already been done - plugs, wires, cap & rotor (if it has a distributor). A new O2 sensor might be a good idea, too, but I would hit the other stuff first. Wouldn't hurt to drop a can of Seafoam in the tank.
 
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Old 11-19-12, 04:16 AM
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Can also be part of a carbon buildup situation. Did you pull the plugs to see what they look like? Color,condition, and is there any sign of carbon deposits. As was mentioned black smoke is normally caused by a rich mixture but based on the car history I would check for carbon buildup also. Black smoke can also signal some spark weakness also. You can run some good cleaning products through the system like seafoam, and even take it out on the highway and give the engine a good punch to try and clean things up also as a first step. It is still anyway an old vehicle and mileage is only one part of a vehicle's life. City mileage is not the same as highway miles and age is age also.
 
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Old 11-19-12, 04:41 AM
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Good point on the highway/city issue. I would much rather have a car with 78,000 highway miles than city mileage.
 
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Old 11-19-12, 04:56 AM
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In addition to the plugs,wires,oil change, general tune up items previously mentioned, you should be aware that your engine has a rubber timing belt, this is not related to the smoke issue but it's very important. It should be replaced every 60K miles on your car. If it breaks, it could possibly destroy the engine. Try to find out from the previous owner if it has been replaced.
 
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Old 11-19-12, 05:07 AM
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Black smoke in an older car is generally carbon.
As others have mentioned, do a full tune up and replace all the consumables (fluids, plugs, etc).
Mopar also makes a clean kit that helps clear out the carbon. It's a 2 can process and the last time I looked, sold for ~$10 at the dealer. One is fuel additive. The other you run the car and spray slowly into the intake, almost stalling the car as you do so, but not. Once you've done the full tune up, a good drive on the hwy to get everything cleared out would be an idea.
It's an old car, low millage or not.
 
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Old 11-19-12, 06:51 AM
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your engine has a rubber timing belt, this is not related to the smoke issue but it's very important. It should be replaced every 60K miles on your car.
Allpar's 3.3/3.8 V6 Engine Page

That engine still uses a timing chain. It's a cam-in-block, pushrod-driven, overhead valve V-type engine, much more like older V8 engines that most of us are familiar with.

The similar engine that has a timing belt is the OHC 3.5L used in the LH cars, LX cars, and minivans.

 
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Old 11-19-12, 02:49 PM
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well, for the year, it's fuel injected, right? far as I know, and what do I know, reason number one for rich mixture and unburnt gasoline is leaking injectors. O-rings and carbon buildup, preventing needle valves from complete closure.
Now, if grandma didn't drive her like she meant it, there sure is ton of carbon build up everywhere, as you got to get that engine hot, to burn it out. Just like your grass trimmer - got to run that engine full rev, or it will choke in carbon build up.
 
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