My 92 v12 just brought me 850 miles and you may have seen my coolant leak thread. Now the leak is repaired, but the day after we arrived the car would not get down the road. It idles fine at 10k rpm but as soon as you hit the gas it has very limited power, sputters, stumbles, misses… I had lost about a gallon of coolant during the trip. The night I arrived at the very end it had good power and ran fine.
Just prior to the trip we replaced plug wires, plugs with NGK, cleaned up the original marelli cap and placed a new rotor. Ignition has been checked and each plug wire shows they are firing.
I now have the car at a local jag shop where owner has a 86 v12 XJS and he is going to replace fuel filter and check fuel pressure on Monday. Had to order a fitting for the fuel pressure kit as it appears the plumbing is new to him.
I’m having trouble thinking this is unrelated to loss of coolant or somehow related to the 14 hr. trip.
I also discovered upon arrival I was low on oil. Oil removed showed no sign of water in the sump. I drained and measured 6 liters of oil.
Car is now holding coolant and has fresh oil and filter. So it seems we just need to follow normal troubleshooting procedures, but am curious if there are additional suggestions to get back to a smooth running state.