XKR Codes Running Lean

[rogermgreen]

Restricted Performance caption. Fault Codes show Bank 1 and 2 Running lean. Engine running very smoothly and performance seems unaffected. Suggestions have been EGR valve (not the solution) and now Oxygen Sensor. Any further suggestions would be welcome.
After re-setting codes the caption seems to return after use of the Supercharger. 1999 XKR 4.0l 90,000.

[J44EAG]

Similar issues can occur with other Jaguar models equipped with a supercharger. My 04XJR at one time had similar issues. Before doing anything else, the first check is the condition of pressure and vac pipes around the super charger for rotting and splitting. Access is reasonable. They are a notorious fail point. Jaguar Main Dealers will sell you a replacement length of OE spec 1/8" rubber pipe or Halfords sell a similar product from their ready rack. In my opinion, the Halfords rubber pipe is the better product as it is thicker walled and appears rather more resilient than the Jag OE product. It is also cheaper! There`s a surprise!!

I suggest you check the two small rubber 1/8" ID pipes. One comes off the SC pressure manifold and runs to the bi-pass actuator. The pipe fits to an inch length of hard, brass pipe joined to the manifold. The rubber PRESSURE pipe in that location can split and fall to pieces. Routeing to the actuator is around the back of the throttle body and a similar hard pipe can be found on the actuator. Just replace that old rubber pipe with new.

The second 1/8" inch rubber pipe is the same material and size is the same type as the PRESSURE pipe just described. This time it acts as VACUUM. The pipe runs from below the throttle body and is located on the throttle body to supercharger elbow. Like the pressure manifold pipe, this vac stub pipe is a short length of hard brass tube let into the throttle body elbow. Again 1/8" rubber pipe figures. From the elbow, the rubber VAC pipe runs to another hard pipe on the vac suction section of the bi-pass actuator. Just rid yourself of the old pipe and replace with new.

Any air leaks for these two pipes will cause fault codes to appear. I recall PO120 and 129 might figure. Don`t blame or condemn catalysts or Lambda sensors before checking the condition of the two pipes described above. If the rubber pipes have failed, then parts costs will be less than a tenner.

Mike K

[rogermgreen]

Thanks Mike, this has reminded me to read again what I think is your article Supercharging Servicing and Symptoms which gives the same advice - on first examination they seemed sound but Ill have another look.. The specialist has suggested the more expensive and possibly unnecessary solution. I really do not want to overlook what might be an obvious answer, so TYVM.

If the pipes are sound what would you suggest further - are there other any other air leaks or cleaning that might be the solution?

[J44EAG]

The MAP (Mass Air Pressure) sensor mounted on the SC elbow could be chock solid with crank case breather gunk! This can upset fueling. It is a push fit sensor sealed with an o-ring. Pull out...push in. That assumes it is not held by the gunk. They can be a struggle to get out. A good clean up with carb cleaner will almost certainly be needed as will the channel and location. They get in a terrible mess after years of neglect.

Getting to the sensor will probably require throttle body removal. Changing the 1/8" ID rubber vac and pressure pipes is made rather easier with the throttle body off the car so its worth doing the whole job in one hit. Get a new crush gasket from a Main Dealer before you start the job. Four long Torx bolts hold the throttle to the elbow. It is likely, the throttle plate, throat and lower regions will again be caked in gunk. Grab a bowl, some rubber gloves, a stiffish paint brush and clean everything up to spotless condition. That will help with engine idle and power output. Ensure the throttle plate snaps shut under spring influence. If it doesn`t, then more cleaning is needed around the plate spindles. Its a filthy job but worth the effort.

Ensure all bolts are tight on the super charger output manifold. If you have the lid off, the rubber and metal sandwich gasket of in good condition is generally re-usable. There were issues with manifold seals on the 4 litre V8 and they can leak badly. Worth picking a set up and replacing those parts if you have everything in pieces.

Its worth looking at some of my engine threads on the X350 section of this site. Although broadly similar, my XJR 4.2 has a slightly different and later generation of M112 Eaton supercharger, the earlier 4 litre V8 Jaguar models are not dis-similar. Whilst the layout has been modified, the principles are the same as for earlier Jaguar supercharged models.

Mike K

[mike020150]

One thing I would add to Mike's excellent list is to check carefully all the air trunking. With age, some parts have been known to harden and crack producing MIL lamp illumination. Mike.

[rogermgreen]

Many thanks to both Mike and Mike!! This gives me something to get my teeth into..hopefully Ill be in touch with results..