Lack of acceleration on 2004 X type Jag - 2004 Jaguar X-Type

code p0121 refers to throttle position sensor(TP) A/ accelerator pedal position (APP) sensor A --range performance problem===causes---accelerator cable adjustment---TP/APP sensor ---wiring
check that the cable is not broken and/ or replace the sensor.

Take the Jag down and get a look at it and get it inspected. Cars tend to spring up on people like this. The light goes off, you check, you think it is fine. But later, it just so happens that it isn't.

ck your coolant for a mixture of oil & coolant & any coolant in your oil. Sounds like a faulty head gasket or bad valve. where any of the plugs wet with oil or coolant? If so head gasket or valves. good luck

check for a blogged air filter,or the breathing diode might have either a leak broken vacuum lines

Hi Richard, I'm not an expert on Jags, just a little jealous I don't have one. Looks like a very nice vehicle. Have a close look, inspecting all hoses and vacuum pipes on the intake manifold side of the engine for any damage or loose fitting. The problem seems to be a leakage of air which is raising the idle speed. Regards John

It may not be the battery, it may be the ignition switch. There is a switch within the key barrel if this switch gets dirty the remote lock, I have a 2004 model. Squirt some WD40 into the key barrel and turn the key a few time to shift the dirt, then try the remote. The switch is design not to lock the doors accidently, so the switch has to closed, when you take the key out of the barrel.

Dealership service only.

i had this problem and thought the fuel filter oil filter needed replacing so i have just had a service done but problem is still there but not as bad. been told it could be the AGR valve or a split pipe going to it which recuirculates unused fuel back to burn again. therefore unspent fuel is coming out of the exhaust causing the black smoke. i am still looking for the answer aswell, hope this helps.

I had the same problem (X-type 2.0d 2004). The stutter was cured on mine by getting the ECU fashed with the latest firmware. This is a known problem and the update does cure it (£28), I didn't bother with all the tests the garage wanted to.
The noisey engine at idle is the alternator belt. It resonates at idle and causes the noise, There is a modified bottom pulley, tensioner and belt kit, but it is rather expensive ~£200 plus fitting (around 4 hours labour). Mondeo's have the same problem but that kit doesn't fit the Jag.
Hope this helps
KB

sounds like a turbo problem. take it to a good deisel specialist. if it's not out of warranty, take it to jag.