I have a ‘15 XKR with about 40,000 miles. It has developed a very random and intermittent surging issue. It occurs after a long drive, at highway speed. It acts like I’m rapidly letting up on the accelerator pedal. Slowing down, it seems to go away. Maybe it was unrelated but I pulled codes the first time it did it, and I got a temporary code “Mass Air Sensor out of range”. So I replaced it…which by the way was kind of a pita. And it didn’t solve the issue…but this time no codes.

My sense is it is not an ignition issue…as the intermittent surge does not cut out completely, and there is no backfire.

Does anyone have a suggestion on how to diagnose this issue, or at least what components might be the likely issue?

 

Could it be the supercharger cutting out and going into limp mode?

 

It's belt driven, there is no other mode.

 

It’s a very quick short term power loss. Thsts repeats about every second.

 

Use a smart phone with the Torque app to read the fuel pressure via the OBD port.

 

It’s a very quick short term power loss. That repeats about every second.

 

Yeah, that was poorly phrased. True the supercharger is belt driven and doesn't cut out. Also true that the ECM will enter reduced engine power mode (aka limp mode) when a problem develops with the supercharger. My question was if whatever caused the MAF sensor out of range code could be triggering the limp mode and reducing the rpms to cut down the work the SC is doing. But that is not likely given the speed of the cycling.

Still operating on the idea that the MAF issue and the surging are related, could there be a leak in the air intake system? Somewhere between the MAF sensor and the SC?

 

Have had this issue with both my 2010 XKR and 2010 XJ Supersport. Got various MAF errors and even an EML. I changed both MAF sensors on both and it fixed the issue on the XJ but I then got lean running codes, turned out that the inlet pipe had a tiny split where it goes into the supercharger so I have one on order. Sky high (25%+) long term fuel trims dropping to sensible trims under load implied an air leak though.

The XKR does it under light load in a high gear, so very low air flow rates. I haven't read the codes yet but I suspect if I look at the long term fuel trims I will see indications of a small inlet air leak, the big inlet tube that goes into the supercharger was shredded when I got the car and I got a 2nd hand one but they are known for cracking and developing air leaks.

100% it's unmetered air causing your issue though. These cars appear to be very very sensitive to that, there is a lot of inlet tracting after the MAFs and it doesn't appear to age well, and the Denso engine management system doesn't seem to deal with it very gracefully.

If you can you'll want to reset your fuelling adaptations using SDD or another diagnostic tool once you change MAFs or undertake any other intake work. I'll update this when I do some more investigative work on my XKR. IN my case once it starts messing around it'll do it consistently at low load high gear until I turn the car off and on again, then it'll be fine. I'll also get crap shifts when it's playing up because it's not able to meter the air and control fuelling properly I assume.

 

I had an issue which sounds very much like this. It would only manifest if I accelerated reasonably hard for a while. For example, joining a motorway/highway and accelerating up the slip road/on ramp, car would pull just fine up through 1st, 2nd, 3rd, but by the time I was at 70-80mph I'd get the surging. Letting off the accelerator would stop it happening. For me it turned out to be a partially blocked/collapsed catalytic converter on bank 2. One of the bricks had detached and slid backwards at an odd angle and remnants of it had become lodged in the honeycomb structure which I guess restricted only at high flow, which was high speed/high gear. Might be worth popping the O2 sensors out and inspecting the condition of the cats with a borescope.

 

Did the car register any codes for this? I'd expect rich running codes, or maybe even something relating to catalytic flow because it knows what's happening before and after the cat.

They are knocking on a bit now these cars, we can expect more weirdness!

 

I would get an occasional P0430, but only once or twice in the space of 12 months or so as I recall. I didn't link the two for quite some time as the code didn't register at or near the occurrence of the surging. I would clear the code and it would be gone for months so assumed it to be the aforementioned weirdness.

 

Hmmm…i recall when I pulled the air box, the foam seal was a bit deteriorated, but I can rembervif the was before or after the maf sensor. Guess, I’ll be pulling it apart.

Wybissue seem to occur after I’ve Ben running at freeway seep for a long time…maybe 30 minutes…then slow down to between 30 to 40 mph and then accelerate…it starts bucking.

 

I'd definitely see if you can get any stored codes from it and look at your long term fuel trims, they'll tell you if you have an air leak after the MAFs without the hassle of getting at the air boxes.

 

Update on the XJ. I replaced the air pipe and still had really high fuel trims and then a lean running EML.

Swapped out one of the brand new Hella MAFs for one of the old ones and the issue went away, so of the two Hella MAFs I ordered one went back because it was so badly made the plug didn't fit and the other one was inaccurate. Replaced it with a new DENSO MAF and the car is now absolutely spot on with long term trims around 0 and no more misbehaving.

XKR also fixed by taking the air intake system to bits and very carefully putting it all back together again, trims on that again back to zero and the surging problem apparently gone.

Interesting both cars displayed identical problems from inaccurate air metering, but from different causes.

 

@XKDreams given the weirdness of our common problem in the "random start issue" thread, i hate to say it, but i just had exactly the same problem. I have a 2013 XKR with 26k miles. I have been enjoying the car since solving the random start issue, hence i took it for a longer drive. I probably made it 30 miles on the freeway when i experienced what i initially thought was road surface noise but then decided it sounded a lot like engine hunting. It only happened when i slowed to 30-40 miles per hour and as i tried to accelerate a quick succession of surges or failures to accelerate correctly. It only happened when accelerating from 30-40 mph upwards, once the revs built it stopped doing it.

To me it felt like fuel starvation, as soon as i built revs/speed it went away.

Its happened twice, both times after 30-40 miles, after parking for a couple of hours it drove home just fine.

I recently had air filters changed by Jaguar specialist, i wont suggest they did something wrong as it happened before and after air filter change.

My next thought is 12 year old fuel filter which i believe is an integral part of the fuel pump in the tank....if i'm going to drop the tank to inspect a fuel sock/filter i'm going to change it all.

Any thoughts welcome?

 

You really need to be able to read codes, see freeze frame data, and look at fuel trims to be able to pin this down. It could be fuelling, air metering, exhaust flow, VVC issues, or ignition causing that. Impossible to diagnose without the data.

 

Next time I drive more than 30 miles I'll have my can tool plugged in. I'm not sure how to record a specific moment in time but I'm sure I can capture it somehow.

 

You should have what's called "freeze frame" data where the car stores all sorts of useful readings at the moment a code is stored, you'll be able to see if there are weird fuel trims, air flow values etc. Any scanning app or too should have the option to see freeze frame data against any diagnostic codes, if you're lucky enough to have the car store a code. Any surging strong enough to feel really should have pinged something.

It can be a proper Sherlock Holmes job though. Joys of old cars.