Every day when I start my 1998 Ford Taurus, the engine shakes for a few minutes. After a short period, the engine speed increases suddenly and the shaking stops. Recently, the 'Service Engine Soon' light has come on, displaying fault code P040
What is the typical cost for a throttle body cleaning service? Could an EGR valve malfunction still be the root cause, and if so, what would be the approximate repair cost?
Throttle body cleaning can often be done at home with proper tools and patience. However, costs vary by location — dealerships typically charge between $50–$60. In my area, a full service including throttle body cleaning and fuel injector flushing costs around $180 CAD. If you're not comfortable doing it yourself, consider contacting several local mechanics and explain your P0402 code and symptoms. Ask them to clean the throttle body and ports first before replacing any components — only replace parts if they confirm that cleaning won't resolve the issue. DPFE sensors are a common failure point on this model, so even after cleaning, you might still need a replacement. Part costs vary but can range from $100–$200 depending on availability. Good luck with your repair — please update if you find a solution. Jeff
Cleaning the throttle body ports and throttle blade is recommended as a first step. Carbon buildup in these areas can cause rough idle and trigger codes like P0402. EGR valve issues are common on Ford vehicles, especially when carbon deposits prevent proper valve closure during idle. However, if the EGR valve were fully open at idle, it would typically cause shaking throughout idle — not just after startup. Similarly, a faulty DPFE sensor should generally result in a consistent misfire or rough idle rather than intermittent behavior. This suggests that the issue may be related to throttle body carbon buildup or transient EGR operation during acceleration.