After having my engine worked on supposedly the Cat worked fine until my husband got hold of her and that lovely engine light and message returned.

We now suspect it could be one of the O2 sensors. He says the 2006 XK8 has four, my question is are they all the same? Also, are there other solutions Cat owners have found to this annoying challenge?

Thanks again. I'm determined to get my car in proper working order so I can then start on restoring the paint by oh at least 2020...

#2018Goals

 

1 x Upstream and 1 x Downstream in each of the 2 Cats = 4. Upstream and Downstream HO2 sensors are different.

I'd get a code reader on it before playing the parts bin lottery.

Graham

 

Advance Auto will run a quick OBD II scan for free. It won't tell you everything the full bore Jag system will but it will tell you the basic codes that all systems must report and it covers the emissions related ones that include O2 sensors.

 

If you are looking for a bit more independence, look into acquiring a cheap ELM327 from eBay or Amazon. This is a wireless device that attaches to the diagnostic port by your left knee (US driver seat). It connects to a phone app for standard diagnostics and live data.

Best of luck, keep us posted.

 

You really need to get the codes read and then post the numbers. We don't care what the reader says the problems are we need only the numbers. Generic doesn't always match Jag codes.. If you are receiving RESTRICTED PERFORMANCE message on the instrument cluster it is not likely to be just an 02 sensor. The codes will give us a better idea of whats happening to the engine.

 

Definitely read the codes. By all means get your own OBD tool...

 

We have an ODB tool and we got these codes: P0171 and P0174.

 

It means both banks are running lean. It means there is air entering the intake that is bypassing the air flow meter. So much so that the feedback system is adding 25% more fuel than per the air measured. It should probably add no more than 5%. You need to go around the entire intake and check for air leaks: intake tube (top AND bottom), dip stick tube o-ring, VVT seals (if you see oil, they are bad and allow air in), all the NORMA connectors from head to throttle body (these take various size o-rings). That is the more comprehensive way to do it.

The other way is to do a smoke test: push smoke through the intake and see where it comes out (the leaks!). youtube has videos for home-made smoke testers. Shops have those, too.

FWIW, these codes do not typically have just one cause. The code come when all leaks add up to 25% additional fuel.

Last, get an OBDII tool that reads the fuel trims. As you repair all these leaks, the trims should go down and restore driveability as well.

Best of luck, keep us posted.

 

Don't forget a lean codes doesn't just mean there is too much un-metered air going in to the engine, it could also mean there isn't enough fuel (or enough fuel but no spark) or the MAF sensor isn't working properly or the 02 sensors aren't working properly.

I guess there is a procedure in the JTIS for troubleshooting those codes?

 

Those codes signify exactly what fmertz wrote and the various things to check are outlined in the svc. manuals as well as some in depth threads on the forum.

Search those codes on the forum, order the appropriate parts book from S.N.G. Barratt (they're free) as it has some very good illustrations of the various components for easy reference as well as prices and they give members a 10% discount.

If that's all you got consider yourself lucky in that there are no electrical or module codes that can be not only difficult to fix but expensive as well.

 

Not disagreeing, but these other causes would likely trigger other codes, too.

The '06 has fuel pressure data available over OBDII, so it is easy to check. From memory, it should be a constant 55psi.

For the 4.2 engine, the air flow meter is cheap and available on eBay. Look for a DENSO 197-6030. I typically do not like to throw parts at a problem, but this is an exception (critical sensor but cheap enough).

 

Maybe just clean the sensor as a first step. Talking of OBD data, they could check what air flow values are being reported before doing anything else.

Also the OP said:-

"After having my engine worked on supposedly the Cat worked fine until my husband got hold of her and that lovely engine light and message returned."

If we knew what work was done it might give some pointers as to what went wrong.

 

The two VVT O-ring seals at the front of the 4.2 engine (on both sides of it) are well-known P0171 and P0174 code-throwing culprits. That was certainly the case last February with my wife's 2006 XK8, and I had installed new ones only a couple of years prior to that time. The engine bay heat gradually bakes these seals, renders them hard and brittle, and causes them to begin weeping both oil and air. When the weep gets bad enough, the codes get thrown. New seals are relatively inexpensive but get decent ones (not the cheapo even-worse version). I installed the third known set of VVT O-ring seals (using OEM ones this time) on my wife's car, and the P0171 / P0174 codes magically disappeared....

 

We cleaned the MAFS and in the process of troubleshooting another issue we disconnected the battery so it wiped out that message on the dash. Now I just have the engine symbol lit up. The work we had done was troubleshooting what the mechanic thought was a hole in one of the hoses, they had the Cat for two weeks looking for the problem.
We did notice there was oil around the VVY O-ring seals so we think that will be the next step. Thanks everyone. Jon89 - where did you get your seals?

 

VVT seals: Jaguar Part# AJ82856. Check eBay.

Get an o-ring kit from Harbor Freight. These NORMA connectors just need to be pinched, and they pull right off. They are sealed with o-rings. Do the PCV valve, too. o-rings again. Each one takes a few minutes to replace. You can do one hose end at a time.

FWIW, people always talk of cleaning the air flow meter, but I have not yet heard of this cleaning actually fixing anything. The air temperature sensor is on the same part. You can compare that air temp with the ambient temp off of the a/c controls. Should be close when moving at speed. If not, it is a hint the whole sensor is bad. Mine was originally 10 deg F off (showing hot) before I replaced it. Now it is more like 1 deg F off, as long as the car is moving.

Best of luck, keep us posted.

 

Thanks. Picked up some O Rings at Harbor Freight, waiting on some from the dealer for the non PCV hoses.

Quick question: How do I remove the O Rings that are on it already?

 

They can easily be picked out using a small sharp screwdriver or a pointed AWL. The really dried out brittle ones usually just crumble to pieces and fall out.