My 2013 rx 350 battery died and had to be replaced. Check engine light and trac off lights came on. Mechanic ran codes and got check engine light off however after driving less than a mile engine light came back on as well as trac off. Took it and left with mechanic and he said code read misfiring. They pulled the engine and replace all three back plugs and coils. $1450 later I drive car one mile home only to have check engine and trac off come back on and at idle car started vibrating and I thought the engine was going to quit. Back to mechanic who now said running rich at idle and it has now been in shop three days and they still have not figured out the problem. Any thoughts?

 

A second opinion from a dealer. There's too much going on here after a simple battery replacement.

 

Any battery can fail at any time, including a brand-new one. You may have received a bad / failing battery. When batteries begin to fail, they tend to start throwing various false codes and warning lights.

 

I agree you may just have a new bad battery, or they screwed up some wires connecting it. There is no reason to pull the engine to replace the rear plugs and coils. You just pull off the intake manifold. That price is also way too expensive to replace the rear plugs and coils.

You need another mechanic who is better skilled at diagnostics and more familiar with Toyota products to check out your vehicle.