alright so a little history first...
1989 jaguar xjs convertible 5.3l v12
a couple months ago my father and i ripped into this thing after he has owned it since 2001 and it always running just "alright" we stripped the engine bay down to the valve cover gaskets. all gaskets have been replaced from the valve covers and up. air system passages cleaned, air pump seals and hoses replaced, fuel injectors cleaned by sd faircloth, gas tanks cleaned and sealed by professional company. new fuel filter, all new gas lines, new spark plugs, distributor fully rebuilt off the car, air intakes cleaned, throttle bodies cleaned and synced, all new vacuum lines, new water pump, etc, etc, etc. as you can see lots and lots of work on all parts of the car. everything was marked and pics were taken. everything triple checked.
so heres the problem....
So my father finally got everything back together on the jag tonight after the injectors, rebuilding the distributor, rebuilding air pump and air lines, gas tank cleaned and coated, air intakes have been cleaned. All new gaskets, for everything from the valve covers up has been replaced and cleaned and most new parts. After cycling the key 6-7 times the gas lines filled up and we cranked it over. She stumbled a bit and finally fired but very very weak and then I gave it a tad gas and it died. After it dieing on us multiple times we finally got it to start and run with the throttle floored!! I mean pegged. Let it go and she dies, won't idle at all. When it's floored, it seems to be running somewhat smooth, like not shaky. But even with it floored it only runs like 1200ish rpms. We are at a loss. While it was floored we turned the idle screw on the air rail in and out and it really didn't change anything. Seems like maybe a really weak spark or not enough fuel or to much fuel flooding it?? We are at a loss. Ever heard of anything like this before or have any tips? He triple checked everything and took his time. The problem is there was so much work performed it's tough to know where to start. Hopefully you have a clue or a starting point for us. Thank you everyone! we consider this an emergency now! haha

 

Have you checked that the throttle spindle clamps are tight and that the throttles are opening properly? And that the capstan rods are properly attached?

Have you set the throttle potentiometer under the capstan to the correct voltage?

Just a couple of thoughts. I know nothing about the Marelli ignition system, so, assuming you have that, someone who does will have suggestions;

greg

 

How long did you leave the injectors after being cleaned?

We had some cleaned and didn't fit them for a few weeks. When fitted they wouldn't open as the cleaning fluid had turned to a kinda wax.

The company that cleaned them said they needed to be fitted and used more or less straight away as other wise the fluid solidifies.

Just a thought.