What are the steps for cleaning the throttle body on a 1998 XJ8 Jaquar?

Having a restoration shop and running several newer Jaguars I have seen similar situations. Intermittent multiple errors such as these can be caused by a low battery (or corroded connections) that "fool the computers". Also had a '99 XJ8 VDP have exactly the same issues over several months. Issue was a manufacturing fault in the sensors on the throttle body that caused the "limp home" mode - usually in stop and go traffic. Jaguar had an inspection and recall on the throttle bodies but that vehicle had gone through 3 different Jaguar dealers for service and none looked at TSB/Recall or performed the necessary checks on the throttle body. Tried cleaning the throttle several times (per Jaguar TSBs) but no change. Had to replace throttle body & problem solved (over 30,000 miles since then). Recommend making sure all air connections to throttle are clean and open and cleaning the throttle area to see if that helps.

On newer Jaguars (and other Al bodied cars) similar problems occur when the "ground" connections to the body become poor (usually through corrosion but sometimes through collisions). Connections may look perfectly normal but have high resistance. Careful when working with the connections - the posts are usually very loosely fastened to the bodies. The engine quit on a 2005 XJ8 VDP when I turned the wipers on (fortunately I was driving slow in a parking lot) because one of the forward bulkhead ground connections was corroded (looked normal but separated from body when removing the wires to clean them).

Also there occur occasional funny intermittent issues with all newer Jags that seem to be untraceable and non-reproducable computer "glitches".Good luck.

The P1722 Possible Cause is:
- Transmission oil level low
- Selector cable adjustment / installation incorrect
- Output speed sensor problem (Refer to P0721 Possible Causes)
- Transmission mechanical failure
Hope this helps.

throttle valve sticking due to carbon build up, remove throttle body and clean out check for smooth operation then re-fit using new gasket

have u had the exhaust system checked for grounding to the body? this is a common source of vibration, the next is hard engine mounts, the rubber hardens with time and doesn't isolate the engine vibration as well, check these items and let me know.

this may sound crazy but what sort of fuel are you running? Try filling the car with premium 98 octane and run it - if you are running inferior grade or dirty fuel the throttle body sensors will register a differential in the burn/energy and throw a fault. The bad news is that a faulty throttle body will cause the same problem and cost a fortune to replace.

fill with 5 gal of fuel, check fuel at motor , looks like tire valve, cover with rag and let evaporate if any comes out before starting 

usually the fuse pannel is under the drivers side dash or under the hood in a black box just take off the lid and on the under side of it usually all the fuses positions are labled

The 15amp fuse for the front cigar lighter is located in right rear of trunk next to battery. SHould ba a black cover over the fuse block assembly.

I had the same problem on my 1998 XJ8. My dealer told me it was the Mass Airflow Meter, which needed replacing to the tune of around $500. After a second opinion at my local Jag mechanic, it turned out to be a hose that was broken on the lower part of the front of the engine. Check the vacuum hoses for breaks or loose fittings.

is the check engine light on ? find dle air valve mounted on throttle body ,remove an clean with spray carb cleaner , or look for vacum leak.