Car drives fine and idles fine but when I smash the gas pedal with sport mode on and traction control off it tends to jerk a lot and worse when cold. Anyone have an suggestions on where to start with trouble shooting this so I can have a smooth WOT. Its a 1998 Jaguar XJR. No fault codes

 

So, I understand that the problem does not appear when in normal mode and traction control on. It is strange that you have the problem in sport mode as this only affects the gearbox, not the engine. Similar is the case with the traction control - it is actually an electronic LSD which deals with the ABS control unit and the rear brakes, should not affect the engine in any way.

Anyhow, you may have somewhat restricted fuel supply. The first thing to replace (if not done recently) is the fuel filter.

 

get an obd reader first not the Bluetooth I had bad knock sensor and the Bluetooth obd tool didn't show the knock sensor get foxwell obd reader or any other high quality reader.

now for the problem there might be many reason
bad sparkplugs-vacum leak-bad or dirty MAF-weak fuel pump-miss fire from ignition coil - and other reasons get obd reader first and read codes then start from there

but personally I would change the spark plugs first denso TT or ngk IX new fuel filter cleaning the MAF and see what happens

 

It happens even with sport off and traction control on too just under WOT conditions. Ive put new spark plugs. Was thinking of doing fuel filter next because its fairly easy and cheap. It legit only does it if I hit that kickdown switch under wot

 

Can you note the RPM the engine reads when the bucking starts and post here?

Are there any warning lights on the dash (amber or red) or messages like 'restricted performance' etc...

Are you aware you can pull fault codes from these cars via OBD connector, on the trans tunnel in the drivers footwell, a cheap OBD scanner can pull these codes, and you can post them on this thread to help us diagnose the issue. At this point it could be many things.

 

I've officially got a gearbox fault code this morning so I guess I got something to go off of now. Any suggestions. Am I able to scan this with obd port?

 

I don't think a generic scanner will do it, but you could stop at a local parts store for a free reading. If you do get a code, report it here, not the generic interpretation.

 

It just threw the following codes P0132, P0175, and P0172 I don't think any of these could cause a gearbox fault tho or am I mistaken with these cars?

 

They can cause such faults on many modern cars.

Only real way to tell is fix the known engine issues and see if the gearbox ones go way.

 

I have attached the descriptions of the codes for you to review. It appears as to have 2 problems. First is an O2 sensor and second is rich fuel on both banks. The O2 is probably not affecting the other 2 codes. Since the problem occurs on WOT I would recommend the problem is with the fuel pressure regulator. At WOT the # 2 fuel pump is energized and a failing fuel pressure regulator would cause over rich fueling.

 

If an O2 sensor is throwing a code it's quite likely the car just cannot do proper AFR (air/fuel ratio) control and any other codes may be junk.