My 09 XF SC has been surging every single time while idle and when you come to a stop it surges once and is normal. While driving it's absolutely normal although once in a while while giving a little gas it surges just barely enough that you can notice. I've cleaned the MAF sensors, the filters, and there was a air leak where the throttle body and the air intake meet, but got it fixed and it's still surging. There was a loud hissing noise coming from the engine before and there still is, but the shop I took it to smoke tested and said nothing came up. He said it's the air pump or something working and it's the sound of it coming internall there is nothing wrong externally, but I think something is wrong. Please help my gas mileage has been crap due to the surging, thanks.

 

Follow the advice about checking fuel trims to see if you have an air leak (as you sound to have).

 

So you think it's still an air leak? I mean he smoke tested it for vacuum leaks and found nothing.

 

You should have your mechanic analyze your fuel trims. WTF is a smoke test? Is that an actual thing??? lol...getting fuel trim analysis will give an indication of your problem way more accurately than a Barney Fife smoke test. Are you sure you are driving a Jaguar?

 

Lol yes I'm sure, and smoke testing is where they hook up a smoke machine to each vacuum like and pressurize smoke through the lines. If there is a leak even small you should see smoke coming out of the line where it's leaking

 

You described my previous problem to a tee. Follow my Threads and see if the solution I tried would help you as well

 

thanks again