i just changed spark plugs in 2006 cadillac cts and its still running bad whats wrongunn
Is it the coil pack
Not enough information. Just too much guesswork. Get an OBDII scan, some parts houses will do it no charge. Write down codes and bring them back here before you buy anything, electrical parts can not be returned even if never installed. Or even packing opened.
The 3.6L does not have a coil pack anyway. It's coil-on-plug. 6 of them. http://www.autopartswarehouse.com/shop_parts/ignition_coil/cadillac/cts.html
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