This is another "stalling" thread hopefully trying to help me and others in identifying the causes.

My XJR recently has some weird starting behaviour. I drove my car for a short distance and then stop for a quick DIY car wash and when finished the car started as usual but then stalled after steering out of a parking spot. Car restarted again alright and again stalled shortly after turning a bend. This repeated a few time so I kept the engine speed through the throttle and clutch to prevent it from dying and car drove normal after a while. No recurrence when car starts cold, only when engine is still warm, typically after stopping and parking for a short while.

Two DTCs emerged upon scanning with the factory IDS: P0331 "Knock Sensor 2 circuit range/performance"; and P1179 "Banks 1 and 2 long term fuel trim too rich (air mass flow rate)".

According to Jaguar DTC, the possible causes of P0331 are, wow, too many:
(1) cylinder head overheat - loss of coolant
(2) wrong fuel type used - low octane
(3) cylinder deposits on Bank 1 & 2
(4) quiet engine with background noise spikes causing retard 1, 2
(5) radio frequency interference affects knock signal, shielding problem with harness 1, 2
(6) ECU fault, knock ASIC fails; knock sensor - group 11
(7) P0326, P0327, P0328, P0331, P0332, P0333

As for DTC P1179, the possible causes are
(1) air leak in exhaust
(2) air low meter high output
(3) ECU fault - read BVC (Battery Voltage Correction) wrongly [lower than actual]; Adaptive fuel group 6
(4) P1171, P0171, P1172, P0174, P0175, P1176, P1177, P1178, P1179

I cleared the codes without fixing anything and drove the car two more days. Problem recurred once but not anymore.

There are however, three suspects.

First is the engine noise. The engine is still noisy as the mechanic is yet to find time to dismantle the supercharger for replacing worn parts and supercharger oil. The engine noise is loudest upon cold start and during engine warm up. Maybe it is the noise that is confusing the knock sensors?

Second is what is common among the two DTCs, pointing to the ECU, which would be difficult to verify, and, if unfortunately so, a headache to deal with, as this one has a special remap by XJRengineer to match the auto-to-manual conversion and neutralization of the immobilizer.

Third is exhaust leak. I believe there is indeed some exhaust leak from the header and/or the downpipes (if folks have been following my story about Rose, I have custom-made exhaust manifold requiring modification to the downpipes). Have to remove the fabricated heat shield and jack up the car to verify.

Before trying to investigate with a long list of possibilities, I would like to know if folks have any idea and experience of such issues.

 

Here is an update. DTCs cancelled and have not re-appeared since. Anyhow, I have refilled a full tank of gas (with Techron) and engine seems awakened. So it could be fuel quality and/or an over-sensitive temperature sensor that caused the stalling. I mentioned temperature sensor as ambient temperature did drop quite a bit when the weird stalling started to happen.