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1989 Sedan DeVille is now just a fond memory ....
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10,459 Posts
That of course is from running rich. Every time you start your car cold your system runs the engine rich until it gets to normal operating temp. That's the simple explanation. If it is excessive then you want to start looking for possible problems.

Has your car been running smoothly? Does it feel like it runs strong? When was it tuned last? Do you drive far enough to get the beast warmed up all the way or do you make a lot of short little trips?

These are all very basic questions that you might address first. There may be more technical causes or problems attributing once these are ruled out.
 

· Registered
1989 Sedan DeVille is now just a fond memory ....
Joined
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10,459 Posts
How is the fuel mileage? Does it seem like it's a little low? Could be an indication of rich mixture which probably shouldn't happen if everything is working properly.

With over 100k miles on it I would first consider changing the plugs at least since you are unsure if or when that may have been done in the past.

Oh, of course, check for any error codes to see if the ECM is tracking a problem.
 
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