Approximately 3 weeks ago something odd started happening with my XFR. I would start the car in the morning, letting it go through it's warmup routine as always, put it in reverse, then slowly back out of the driveway. During this time, the car would hesitate, with an rpm drop like it wanted to stall, but it never did.

After backing out of the driveway and putting the car in drive, it never hesitated like this. I've noticed is that the idle is a little "off" in that it doesn't feel rough, but isn't buttery smooth either. What's doubly odd is that the engine is pulling stronger than usual, as if it's in dynamic mode, though that isn't the case. It stays in gears longer than usual for some reason, though shifts are still smooth.

I've noticed is that occasionally I will see the average mpg display drop noticably -- one time I watched it go from a rather solid 15.6 mpg down to 14.1 over the course of a 9 mile drive. And this was to a rolling average based on over 2000 miles of driving. I have since reset the counter and it has held pretty steady.

And today I noticed that sometimes if I rev the engine and let my foot off the gas suddenly, the revs don't start to change until 1-1.5 seconds AFTER my foot was off the gas.

Dealership cleaned the throttle body but it made no difference. In fact, I'd say the problem has gotten worse since then. They suggested we try replacing the MAF sensors, but I wasn't going to give them $1100 for parts and labor based on a guess.

All this and not a single code! Any ideas what might be going on here?

 

$1100 to replace the MAF sensors!!!
They are taking you for a ride, they take 10 minutes tops to replace and shouldn't cost more than $100 for a new pair, heaps on Fleabay at around $50 each.
Worth a try to clean them yourself, a 10 minute job, just get a spray can of MAF sensor cleaner.

 

I know, right? That's why I declined the repair.

I cleaned them and it made no difference. Have one on order and will see if it makes any difference. I'm doubtful, but for $55 it's worth a shot.

 

Have a look at fuel trims using OBD live data. A small air leak is most apparent at low revs / idle.

May as well watch MAF values in case they're odd, but it's not very likely.

 

If your battery is good, and no codes, try doing a hard reset on the car by disconnecting the positive cable over night. It's free and easy.

 

Similar thing happened to me. Started my XF in the morning and felt like it was struggling to reverse out of my drive way. It felt like the brakes were sticking slightly. I didn't look at the rpms.

 

Any chance it could be carbon build up from the DI system?
Have you had a Motorvac service done?

https://www.motorvac.com/index.cfm?id=66616

Just a thought?
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Is the check engine light on? In any event, did you scan for codes, both current and pending?

 

Sounds very similar to my situation, especially what you mentioned about brakes sticking and erratic gear changes. It's consistent in the mornings and during the day the symptoms come and go as they please.

If you make any discoveries, let me know. I will be sure to do the same!

 

No CEL ever. I'm going to order a code reader and see if anything shows up, though when the dealership had it a couple weeks ago they said no codes found.

 

I ran a can of BG44k though the system a couple months back and the dealership put some sort of cleaner in the tank last time it was in. Symptoms went away for a week then came back.

 

Yep. Planning to get an OBD2 reader.

 

Yes, cleaned them. No difference. Just tried checking for vacuum leaks with carb cleaner but did not find any.

 

Hey Oz do you knkw where exactly i can get two MAF for that price for my 2010 xfr, i jave a code that says bank one, but i would like to change both.

 

On checking it looks like I might have led people astray.
It seems all the cheap ones on Fleabay (eg here: https://www.ebay.com.au/itm/Mass-Air...QAAOSwtGlZBFE9) are used, not new, which means there is no guarantee they are any better than your existing ones.
The new ones (eg here: https://www.ebay.com/itm/Mass-Air-Fl...pZfx4-&vxp=mtr) cost a lot more, US $176 and higher.

 

Remember you have a DI engine so putting things in the fuel does no good at all for carbon build up. You MUST use a product that is sucked into the intake system so it can get to the intake tract and most importantly the back side of the intake valves.
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so then what do you recommend?

 

Did you look at the link I posted?

It has the products listed by name and part number and I would at least try one bottle. I can't see that it would hurt anything?
Just remember that you can't dump it in the gas tank. You need to have the engine running and use the engine vacuum to suck it in thru the intake tract. The bottle will have some basic instructions on it.

If you do try it please post back as all of us with DI engines will run into this at some point. I don't know if regular cleaning will help or not? Some engines require dismantling to get at the carbon.
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Maybe that's what the dealership did. I don't think they specified what sort of cleaner they used.

 

So, got a code reader. Not one. Damn. Code.

I also looked at the data from the engine and nothing is out of the ordinary. Fuel trims are good, data from the MAFs, O2 sensors, etc are all nominal.

I speculated that there could be a vacuum leak and whipped out a can of carb cleaner, but it did not reveal anything.

I'm at a loss here...