Hi all,
Lately my 2006 XJ8 has been pinging more than I remember. It always gets Amoco 93 fuel and still has plenty of power. No idiot lights have come on so that is good news.

I had the transmission selector switch in economy or normal mode for the last month or so, then this weekend I put it in sport mode. Now the pinging has gone away.

Does the transmission switch also change the engine timing? And is it normal to hear pinging in economy mode?

TIA,
John

 

There should be no pinging heard, or actually happening, in this engine, regardless of octane used, within the range typically sold at fuel stations. Knock sensors prevent that from happening as a primary part of engine management. Knock sensors are known to fail, but will set a P fault code, either P0327/8, or a P0332/3, but you would know it because it will default to restricted performance mode along with the codes.

You have to be hearing something else. I'm curious as I don't know of anything offhand related to transmission sport more. Can you give more description? What are other conditions? Cold engine/warm? Startup only, or constant? Does the pinging frequency match RPM or speed, or stay constant? I'd like to follow this one.

 

The pinging is only when the engine is at operating temperature and lugging in a high gear before downshifting, or under light acceleration. Again, this only happens when the transmission is in the econ shift mode. When the transmission downshifts the pinging stops.

I called my Jaguar dealer and the service rep advised that I fill the tank with fresh gas as he suspected water was in the fuel. Stupid me, I went back to the same service station for a refill...

Hope this helps in diagnosis-

John

 

Try a tankful of higher octane-rating fuel. If it disappears you know the problem.

 

93 Octane is as high as it gets at gas stations and exceeds the recommended 91.

 

US fuel octane rating is certainly very low !! Here in the UK we have 95 as the norm and 97 available. Do the US Jaguars have lower compression to compensate ?

 

Fraser,

Octane is measured on different scales in the US and Europe.

[edit] Research Octane Number (RON)

The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.
[edit] Motor Octane Number (MON)

There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load as it is done at 900 rpm instead of the 600 rpm of the RON[2][3]. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally, fuel specifications require both a minimum RON and a minimum MON.[citation needed]
[edit] Anti-Knock Index (AKI)

In most countries, including all of those of Australia and Europe the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries,[which?] the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI). It may also sometimes be called the Research Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2.
[edit] Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.

 

Now that I have been driving in Sport mode for over a week, I am still able to detect a very subtle pinging. It is when the transmission is in a high gear and you give it light throttle, like driving around town. It never lasts over 2 seconds. As far as location, I would have to say it sounds like it is coming from the right bank, but it is really hard to tell.

I took the plastic top cover off the engine and listened while idling. The corrugated hose that runs from the intake manifold to the PCV valve has a loud hissing sound as detected by holding a length of spare fuel hose to my ear. This may be normal, but worth mentioning.

John

 

Hissing sound could indicate a leak in the pipe which would be air bypassing the air flow meter, thus causing weak mixture and..............Pinking !!

 

How many miles on the engine?

Carbon buildup maybe...

 

The hissing sound is normal from the chrome round object on the top of the enigne. Thats not a air leak.

 

The car has 54,000 miles. As far as carbon buildup, I don't know. I ran a large bottle of Techron through the engine a few weeks ago.

The hissing is most definitely from the corrugated plastic hose from the intake to the flat black plastic PCV on the right camshaft cover. Since it is corrugated, I suppose the airflow alone would make it noisy.

John

 

Best way to test is spray some carb cleaner around the area. If your RPMs change, you have leak.

 

My '06 does the same thing! At a steady low speed (30 MPH) with the window down & no radio on, I get a VERY brief (1 second) pinging, or "rattle" sound when I dip lightly into the accelerator. I goes away immediatley, only to return again when I repeat. I think it doesn't always happen, but couldn' swear to it (can't hear it w/ windows up/ radio on.) I ALWAYS use Shell 93. I'm guessing that the anti-knock sensors are "catching" the knock and dialing back the timing, as designed. Am I right?

 

It's good to know my car is not the only pinging XJ8. Your car's symptoms are the same as my car's.

John

 

Fastexas,

The knock sensor should act far more quickly and far sooner than being able to hear the pinging temporarily. Unless the sensor is on its way out. I've seen some frequency of failures in X-Types. Can't say I've sen much on the AJV8, but I don't see the volume of vehicles a dealer would see.

John,

Something from your post above, when you added the Techron did you add a full tank of gas? I am an avid believer of Techron and I use it twice a year in my own cars, but it is very powerful stuff. Too concentrated and it can cause rough idling/running. Additionally, Techron can do damage to the intank fuel pump in highly concentrated amounts. Love the stuff though.

 

Steve,
The Techron was in a full tank. It's the first time I've used it in this car. Since there is another '06 with the same issue, I wonder if is an issue with the engine management program or a bad run of knock sensors that year.

The service representative at the Jaguar dealer said he has never heard of pinging with a XJ8, but he said the S types occasionally come in with this issue. I am not excited about paying the dealer to find a problem then fix it so keep the ideas coming.

John

 

Hi John,

Yes, I am the same as the dealers. Pinging is a new one to me even back on the 4.0Ls so I'm hesitant to continue to try with solutions. I don't like guessing and usually will only bring forward solutions I know I've tried problems I've solved.

Back in 1988, I bought a new BMW M6. Regular use of Chevron Techron was a warranty requirement in the owner's handbook and I've used it ever since. In my area we have Chevron stations with Techron already in the blend. I only use Chevron in my Jaguars, then do a supplemental treatment about every six months. I use the large size bottle split between two Jaguars with full tanks. I think using it can be overdone. I know it is hard on rubber seals so correct concentration is important.

 

I still notice the pinging even in Sport mode, but less so than in Econ mode. It lasts about 1 sec. then disappears. Will this damage the valvetrain over time? I would like to quit straining to hear the noise and resume enjoying the driving experience of my Jag!

John

 

I have found that once I have heard a noise, even though it may be repaired, I will listen for it for as long as I owned the car.