The Check Engine Light can illuminate with codes due to the lack of EGR (exhaust gas recirculation) flow caused. This is commonly a result of a clogged passage in the intake manifold. To correct this problem, the EGR valve has to be removed and the passage cleaned thoroughly. Partial restriction of this passage can cause smog test failures for the NOx emissions without causing a drivability symptom.
Check Engine Light Due to Plugged EGR Passage on Mercury Mystique
Average mileage: 116,170 (86,000–135,000)
Exhaust & Emissions affected: 2.5L V6
18 people reported this problem
1996 Mercury Mystique 113,000 mi, Visitor
flashing check engine light ,replaces egr valve all is ok now
EGR Valve and pressure sensor failure, check engine light, takes several trys to start, acceleration is poor, bad MPG.
I had to have Precision Tune to clean the EGR valve passage and afterwards it passed the emissons test with a new EGR.
1998 Mercury Mystique 101,301 mi, Visitor
they egr passages were cleaned, egr valves replaced two time, and the check engine light is always on???
1997 Mercury Mystique 127,890 mi, Visitor
Ken's Tire in Livermore correctly diagnosed this problem. Carbon was packed so solid they initialy thought they were going to have to take off the intake manifold to clear it from the passage. Now I wonder if this was the real problem 60K ago when Pacific Ford in Long Beach charged me $3200 to replace the catalystic converters. I'm the original owner of the car. It's been pretty trouble free except for a replacement automatic transmission at 85K. I've been pretty regular with dealer maintenance until I moved to Livermore.