Question about 2003 Mercury Grand Marquis
Check the EGR/DPFE sensor. They are all one piece for the 03 and newer models. I had the same problem and after replacing inectors,coils and plugs I still had the problem. If there are no vacumn leaks then this may be the problem. Try to clean the EGR and MAF sensor and if the EGR is really bad then look into the OEM replacement part since alot of aftermarket units trigger Check engine light. Try to search for DPFE problrms online and you will see that this is a common problem.
Posted on Aug 16, 2009
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Posted on Jan 02, 2017
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