As the title says, I was just about to sell my 2004 XJ8 with 166000 miles and the dreaded "faults galore" issue occured. I have window wipers that are going on, on their own. Engine systems fault, abs fault, dsc not available, and the car will randomly shut off after driving for a bit. Vry scary stuff. That said, after doing some reading I went ahead and bought a used throttle position sensor. I changed it out and cleaned the throttle body as well. Unfortunately the problem persists. I thought maybe the used sensor was defective as well so I ordered a new aftermarket sensor and now the cars idle is more erratic and the problem persists! Please help!

 

I'd have the alternator and battery checked.

 

Sounds like a problem that an only an IDS/SDD setup could diagnose assuming, of course, the battery is ok.

 

Check the earths particularly those behind the headlamps.

 

What nit624 said.

 

Yep,
i) Battery
ii) Earths

 

Thanks guys! I'll check the earths. I thought it may be the battery so I bought a brand new one just in case but still nothing. I'll update soon

 

Try the ECU reset with the cables disconnected from the battery and touch them together for 30 secs or so.

I was going to say battery, but you already had that covered. Don't forget the earthing points in the boot too (trunk).

 

Check the charging system (alternator) output. I just had weird things going on also as you have, including the cooling fans running with the engine cold and 16f outdoor temps. put new battery in, no change. Checked charging system, voltage was good then bad, then good (intermittent). Changed alt, and all went away and is good to go.

 

Thanks to your help guys! I was able to resolve the issue! Turned out to be the earths behind the passenger side headlight! Created a new ground and the car is purring again! Can we change the title to say RESOLVED and can I get an AMEN?!! LOL

 

Excuse my ignorance, but can some one explain (or link to) what the earths are? Can't find this info anywhere.

 

Also known as "Ground"

The Brits just complete the thought. In the US, we say ground, which is to say a return to a direct physical connection to the Earth.

 

exactly the same problem I am experiencing. would someone kindly snap a photo of the grounds please just so I can orient my search.

Thanks in advance!

 

You can see two nuts for two ground attachments behind the headlites. Same both sides.
Apparently they break very easily indeed.