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Cadillac Deville Failed Smog For High HC

I own a 1996 Cadillac Sedan Deville. It failed the smog check for high HC. Everything passed except this problem.

I need to know what to do next. I got a tune-up, got the ignition moduel fixed, and the coil pack. One smog technician says too much HC coming from the tailpipe. Another says my Cadillac is running too hot. Were do I go from here? I bought this Cadillac Deville in 2010 and it ran fine. Then I went out of state for a year so it set up when I got back I ran it for a while then took it to pass smog check and it failed. Can you help me get to the root of the problem? Thank you.

Answer:

Hydrocarbon (HC) is basically raw fuel, otherwise known as gasoline. The main reason your Cadillac Deville would fail the smog check because of high HC would be defective spark delivery, but the fuel system has a lot to do with it as well. A "rich" or "lean" fuel mixture would contribute to high HC as well. You should first inspect your Cadillac Deville's ignition system, ie. spark plugs, wires, distributor, ignition timing, and if everything looks ok, move on to the more complicated inspection of the fuel delivery system, ie oxygen sensor (s), engine coolant temperature sensor, mass air flow sensor. These components will require some auto emissions know-how and proper inspection tools. It is best left up to a smog check technician. Follow the link below for a full list of High HC Causing Problems: What Causes High HC? posted by SmogTips Support

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