I have a 2004 TL with 75k miles. In recent months I've noticed sluggish performance in acceleration. The engine seems to "flutter" when accelerating, notably in the 30-35 mph range where you can actually feel the car shimmy. When the car is driven hard I notice a sulfur or "rotten egg" smell frequently. Also the overall MPG is slightly lower (2 to 3 MPG) than it used to be.

I've just had the belts, transmission fluid and spark plugs replaced. This has helped a little but the symptoms described above are still present. I've always used 91 octane gas, get frequent oil changes with full synthetic and also use Seafoam in gas system a couple times a year. I've tried to reset the computer (turn key to position II and hold down gas pedal for 30 secs.) but this hasn't helped.

Any suggestions would be greatly appreciated!

 

that may not be the engine but the transmission hesitating on shifting... Have you ever changed your 3rd and 4th gear pressure switches?

 

Your app sensor may be on its way out, surging, hesitation and fluttering are all classic symptoms.

 

I've not replaced these switches but will look into it. Is it costly?

 

Is it worth replacing this sensor proactively?