I am having this problem. Installed the 74 mm throttle body and MAF ( putting the original MAF sensor in the new MAF body) and the car idles fine when first started. however, after a bit of driving the idle will go between 1500 and 2000 on neutral. if changing gear, it will accelerate itself after pressing the clutch. I used the black RTV gasket maker along with a new oring on the throttle body. I guess its back to checking the connections and re adjusting the throttle body. Hope this gets solves.. i dont want to go back to 68mm...

 

Based on my personal experience, and that of several others in this thread, I would try to just put some miles on it before messing with everything again, if you feel you installed it correctly. Several of us have simply needed to let time pass and the cars ECU to adjust to the new part. That is the only way I can explain it as I did every test in the book on mine, no vacuum leaks, no nothing and it was surging. I drove it a few hundred miles and have not had any trouble since.

Just a thought...

 

I will do just that, If i see no improvement I'll take a sealing expedition into the engine bay next weekend and see if that helps. I'll update as soon as I get some feedback.

Thanks a lot!

 

It is always puzzling to me when I see people with problems on the change to the 74mm TB. I did it along with the larger air box and intakes and had no problems at all, I did not even notice an adjustment period or a hiccup. There must be an explanation though, is it because the air is insufficient without the air box and intakes? I thought everyone was changing the whole set up.

I think that the changes are quite subtle anyway, it took the tune to see a real difference and that definitely took a couple days of driving to feel the full benefit.

 

Being an automatic.. mine seemed to have some very minor surge issues at first (extra second or so @1500 rpm when coasting to a stop). The only other intake mod from OEM was the K&N filters. And the performance difference was good for a little extra giggle or two when accelerating from a stop.. Did it by "the book" here, probably took twice as long as most.. I was in no hurry and 100% right the first time was the goal.

 

Max and I talked about this at length and had some theories, but just that, theories.

I would say a solid 30%, if not more, have had surging idle issues with the swap. After spending a day doing every test in the book on mine and knowing it was correct I finally said screw it and left for the Dragon with it surging. It did it once or twice while I was there, but I think I flogged it hard enough to beat the ECU into submission...

 

Did you make sure to swap out the 68mm MAF sensor into the 74mm MAF housing? This will cause a number of hiccups in the installation and will make it run erratic as well.

 

GG, he stated :
in the first post ......

( so there - I done a 180 on ya ! )

 

Thanks George, thats what I get when I go to bed at 4 am only to wake back up at 5:50 and run around the house... When I did mine, it just went through a very little learning portion, then its been settled down since. Runs GREAT and no problems.

 

Dave ( onehundred80 ) is always correcting me on my stupid mistakes, feels good to be able to do the same from time to time.

 

BTW my friend, if you ever travel to Myrtle Beach SC you would have to pass pretty close to my house. Give me a call and we could share a couple beers and maybe a story or two. Just an invite, which also extends to any other XF owner who may pass close by!

 

well i have been driving it yesterday and today, and it is idling correctly as of today's drive to work, but I will see how it behaves during the rest of the week. thanks for the support!


Update

it settled now. little by little. I did take the Assembly apart and made sure every connection, including the MAF, MAF elbow, throttle body, oring, ETC, was correctly in place, as well as readjusting the throttle body screws ( do not overtighten, my torque wrench broke one way before 7.5 lbs were reached... it was a ***** to take out and eventually had to have a friends mechanic pull it out...)
it runs like a champ and I love this mod.