I have spent over $6000.00 on a 1998 Lincoln Navagator over the last five year at Doctor Auto. It became apparent they are only about making money. I just took my suv in for a tune up it continued to have a problem. A few weeks later the engine light came on. They charged me $110 for a diagnostic and the service was for a $10 part. About three days later the check engine light came on again. This time they said I needed a catalytic converter for $1500. I picked up my car and took it to AA Auto repair. The cost to repair was $360 for two sensors.