All, I have a 1975 XJ5.3C which is a very good original car (68k miles) but last couple of years not really smooth running.
I have checked / cleaned / replaced injectors
Replaced engine harnesses
Replaced dizzy cap, dizzy arm, plug leads
Replaced all capacitors in ECU
Coolant temp sensor swapped
Tried swapping coil
Tried swapping ECU for a NOS ECU
Checked fuel pressure with a cheap and simple gauge and seemed OK
Checked timing at each cylinder at warm idle and no obvious spark missing when engine falters for a second or so
Still lumpy idle and not turbine smooth at higher rpm either, accel definitively rough compared to earlier form. Usually it runs quite well just after a cold start. Most often it is the RH bank which is lumpy. The tell tale exhaust pressure against the hand is usually smooth from the LH bank and lumpy from the RH bank. Engine temp OK at all times, idling in a queue on a hot day with AC running and motorway runs for hours all se a nice stable temp with the needle just below “N”.
The mostly RH bank symptom in my opinion excludes the ECU and amplifier as IIRC each output drives six cylinders, three on each side.
Heads have been off and cleaned / checked.
It should be noted that running a slightly later ignition than per book gives more power but a slightly rougher running, no other ill effects to be seen.
That leaves two possibilities in my mind:
- General under fueling
- Ignition problem mostly related to the RH bank
Can anybody shed any light on this based on your experience?