Hi all,

I am having a huge problem with my Jaguar XKR, 4.2 V8, 2008.

When I accelerate (hard):
1) Once revs are above 3.5-4k, I feel a loss of power
2) Once the revs reach 5-6k, I hear a "skipping?" sound...
(Like a flag sounds when a strong wind is blowing!)
3) the higher the revs, the bigger loss of power. And by loss of power, I mean that I literally cannot overtake!

4) I cannot hear any "suspicious" sounds, when in low revs. The effect takes place when at high revs.

I tried to have it serviced, and the mechanic thinks it's the supercharger.
He said that he opened the supercharger and found signs of wear. But he cannot guarantee that this is the problem. He recommended trying a new supercharger (at a huge expense of course).

Before I go down this path, I would like to ask you
1) if the "symptoms" I describe point to the supercharger, according to your opinion,
2) or could it be the transmission?

3) what should the mechanic check, before I start buying expensive replacement parts?

Thanks in advance for your help!

 

He "opened the supercharger"? That wouldn't be a small bit of work for a "let me take a quick look" kind of deal. It'd be at least a few hours labor for in-and-out, so he must have charged you $200-300 for that diagnosis?

 

My Alfa Romeo 164 made some similar sounds - ignition leads were breaking down.

I would look at the ignition system - basically you need fuel and sparks working right - I've never had a turbo or supercharger issue so I'm not sure what they would sounds like when misbehaving.

 

Is the MIL illuminated and if so, what DTCs are in the system?

Has any work been done on the engine and associated components?

 

Also can you post a sound clip so we can hear the exact noise its making

 

Well, he hasn't put it back yet... But I expect this diagnonis won't come for free... :P

No check engine light. No specific error logged. ECU thinks it's all great...

If ignition was failing, shouldn't I get something on the ECU? Even as pending fault? Misfire? etc???
This whole thing (noise + power loss) does not appear at all on the ECU.
Engine has not been opened (yet).

I'd really love to, but the car is already "opened". So I cannot record anything at the moment.

----
What the mechanic mentioned is that he found signs of wear inside the housing and on the blades.

If you can think of other potential causes (which could be cheap to check at least), to make sure that I eliminate potential causes... Before ordering stuff for the supercharger...
-Would changing transmission oil help, if there was a problem with the transmission? Would a problem in the transmission, have such symptoms?
-If there is a problem with the supercharger, could this kit maybe help?
Jaguar XJR XKR S-TypeR Eaton M112 Supercharger Snout/Nose Bearings Rebuild Kit | eBay

 

You mentioned a transmission oil change does the tranny feel like it's slipping?

This flag noise you speak of is it coming from the engine bay?

In regards to your supercharger i know the amg 5.4 has issues with the idler pulley causing the belt to slip and high rpm what's the condition of your pulley?

 

I'm wondering if fuel (pump/filter) might be the cause.

Or coil(s) due to the high load.

You're lucky if you get codes for the above.

 

I kind of think tearing the engine apart before you tried anything else was kind of a bad idea. As someone said, it could have been a coil and a five minute job.

 

Is your tech a Jaguar dealer tech or an indie? If he is an indie, does he have all of the Jaguar diagnostic software? This should have been used before tearing into the super charger.

Your description and the revolutions involved sounds like something I have heard before, but it is not supposed to happen with the car in motion. Jaguar has a rev limiter to prevent damage to the engine when in neutral or park. If this is the case, I would take it to a dealer to be checked out.

 

Well I can't really tell if it's the transmission or not... It sounds like it comes from the engine bay. But as a precaution, I think it's a good idea to change the oil. After all, I;ve seen that it's advisable to change transmission oil at ~60.000 miles...

The mechanic also replaced the belt, and said there was no improvement, so he did not think this is the cause of the problem.

I have not seen any fault codes. Generally there are absolutely no error codes. I would expect that something would appear if fuel pump was the problem...
That said, I will ask whether the mechanic has looked at the fuel pump or coils.

The problem appears only when on the move.

The mechanic is not a dealer. I am greek, and the car is at the moment in Greece. And generally jags are not very popular in Greece. Which means that even the dealers have no idea how to work on them (I know it from personal experience). Therefore I decided to go to a mechanic I can trust, who admittedly does not have experience with XKRs (but neither the dealers does...), but at least he is willing to go the extra mile, without ripping me off...

------
What I forgot to mention is that once the supercharger was opened, he found some "bits" inside.
After "cleaning" and refitting, he said he noticed an improvement, but the problem was still present.
And this is why he insists on the supercharger.

I have already ordered the transmission oil to be replaced, and a reconstruction kit for the supercharger, before I try replacing it completely...
Jaguar XKR 4.2 litre Eaton M112 Supercharger Bearings Rebuild Kit 2008 2009 X150 | eBay

I will forward the suggestions about coils - pump.
And any more ideas are more than welcome!

 

Please note I am a total newbie to these cars, however,

I recognize this symptom as something that happened recently with my Porsche 928. This was caused by a failed mass air flow meter. The way it happens is, the MAF is reporting far too little airflow when you are actually sucking a lot of air at high rpm under load, and then the computer responds to this false signal by starving the engine of fuel. The computers don't know anything is wrong because the code self-diagnostic system has no way to check if the MAF is calibrated. It just assumes the MAF is perfectly calibrated and goes from there.

 

On modern cars, fuel trims should show if it might be a MAF doing that. (Of course the 928 doesn't have OBD II.)

 

Buy yourself a cheap Bluetooth obd scanner and install TorquePro app, you can see many engine functions with it, fuel trims, supercharger boost pressure, AFR ratio, and so on,...

What your describing can be a restriction on the intake or exhaust side just a guess..

 

This is the first thing I did when I bought the car!
I have actually 2 scanners. One specifically for this model. (and of course much more expensive).

No faults have been logged!
ECU has absolutely nothing to show.
No misfire, no faulty sensors (shown at least)...

I am considering about changing coils, but they are quite expensive.
And I would have guessed that something would have appeared in the ECU if the coils were not performing....

 

So... look at fuel trims.

 

Sounds not unlike the problems I had with my XJR.

Loss of power at high revs, "sounds", etc...

https://www.jaguarforums.com/forum/x...solved-137070/

After chasing my tail it turned out the catalysts were choked up.

 

Why do Jaguar cats clog up? Porsche 928 cats last longer and don't clog. Only reason people change them is when they quit scrubbing NOx effectively, which happens usually towards 200K miles.

 

It looks reaaaally similar...
I have notified my mechanic to take a look at the cats, before continuing...
And he told me that he had "opened and cleaned the supercharger", but also "cleaned a bit the o2 sensors on the cat".
And after this, he saw a bit of improvement. This lead him to believe it was the supercharger, but it could have been also the cats...!

Thanks for the info!

 

I suspect the 928 ones are not to anything like the same spec.

Generally all fail eventually, but that can be 20 years or whatever so not many of our cars have failed yet. Many that have failed have had engine faults - often uncorrected ones such as poor fuel trims not throwing codes but hey does anyone actually check them? (Yes, a few of us.)

The jag PCMs are far better at flagging codes and are (due to law changes) able to see faults that I am fairly sure the 928 does not (not being OBD II).