I had what sounds like a similar problem with a slight hiccup and occasional rough idle with my 1995 XJ6 4.0
I replaced coils, no change, replaced fuel filter, no change, replaced relays, no change, replaced throttle position sensor, no change.
The hiccup was not predictable and happened at times where I would need to pull out into traffic quickly.
No error codes were showing up. My mechanic was baffled.
I bought an ECU for a 1995 XJ6 that had the same # but different software revision.
Cured the hiccup however the car did not run very well and check engine light would flash and remain on.
Finally I bought a good used ECU unit on EBay with the EXACT same number and revision as the one in my car.
That cured it. Very easy to install myself too. Car has run great ever since with no problems.

 

When replacing the ECU the TPS has idle stop value of 0.60 +/- 0.02 volts DC

This can be at .0.58 to 0.62 in theory

The ECU is adjusted to the value of the sensor at this idle stop , this is referred to as orientation of the ECU

When replacing a ECU the orientation setting to the TPS may not match

There is a easy way to get the new parts configuration to match

There is gumming of the butterfly that prevents the making it to mechanical idle stop along with throttle return spring shortfalls putting it there , this is both common on this engine

 

If you have a noid light you can check to confirm that each injector and coil is being grounded by the ECM.

 

It could be the ECU but i haven't proven that to be the issue as of yet. Looking at the diagrams i can't even tell where it is. Looks like you have to take out dashboard, front quarter panel and a host of other stuff. The manual is better than nothing but its about as clear as mud in places.
Don, i have no noid light nor do i know what it is. Never heard of that.

 

Anybody know who made the ABS control unit for this car ? Bosch perhaps ?

 

It is possible the ABS control module was manufactured by Bosch, Siemens, Hella, etc., but if memory serves the label is marked Ate, the German company founded by Alfred Teves, a pioneer in disc brakes, anti-lock brakes, etc. A very common issue with these control modules is starved, cold or cracked solder joints on the circuit board, particularly at the two large pins that serve the pump. But this should have nothing to do with your flashing CEL. Unless I missed it, you have not reported any of the DTCs associated with ABS module problems.

Cheers,

Don