" Fuel pressure, measured on a test gauge, will vary between 2.7 bar (39 psi) at idle to 3.1 bar (45 psi) at full load to compensate for intake manifold absolute pressure "

on page 58 varies with manifold vacuum line

 

You may have some metalic debris on the CKPS throwing off your timing but not giving you a code

See page 35 of the 881 Jaguar pdf for location pics

 

Hello Parker,
Wow! What a wealth of knowledge you have!
The car is a 2003 XJR and has the AJ27SC engine. I think today I'll up the pressure to 41lbs and see if that has a positive effect. I need to run some errands this morning and might as well take this car for a test run. If it works or not, I'll let you know....

 

Drove only about 10 miles and no code but it usually does not usually happen until I have about 50 miles on the car. Will be driving it again this weekend will let you know if all goes well.

 

But of course the codes returned! (P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P1316). I moved the pressure up to 42lbs and still got the code and same result at 45lbs. I had mentioned I never noticed any misfire though this time I was paying close attention to the car/ engine and it did have a very slight stumble occasionally while idling. Not every time but a couple times I sensed it happen. Tach dropped a bit and the engine sort of briefly shook a tiny bit for I'd say less than a second. Perhaps that is the misfire? Perhaps it's not the fuel pressure regulator but something else? The regulator replacement certainly has not resolved the problem.
Apart from this stumble, the car idles very smoothly and accelerates quickly without hesitation.

On my other cars the same short of thing happens at times and there's not a CEL, or if the light comes on it goes off very quickly. Usually this might happen right at start up though.

 

I’m just grabbing at straws here but, have you checked the condition of the ground cable under the engine at all? After the engine has been on for awhile, are either one of the battery terminals hot to the touch?

 

Adjustable fuel perssure is always adjusted when vacuum is disconneced or engine is not running while fuel pump is on. Only this way that propotional correction works as it is intended. Running engine while adjusting pressure without vacuum line causes vacuum amount too low fuel pressure.

Are fuel trims okay all the time even when the money light turns on ? What does the both downdraft lambda signals do when driving ? It needs to be rembered that misfire code is kinda flawed. Misfire will be pinpointed with knocking senors and calculating engine rpm defiency per cylinder. The exactly same symptoms can be caused either missing spark or missing or execss fuel in cylinders. ae sticking open or close injectors. Mostly injectors that sticks shut. Look for Ford module v8 fuel injector failure symptoms. Those has injector failures. I even had experenced that by myself with one Lincoln Towncar. That lincoln started to misfire ocassionaly in the trafic lights throwing misfire codes on random cylinders. Every time misfire went away when I switched to neutral and stomped to the gas pedal. Why ?. More current to the injector coil has more power to unstick the injector.

To drive steppermotor you have to have logic driver for it. It is driven by energizing on of the coils per time in correct order.

 

I did set the pressure with the vacuum line attached so will remove and recheck it again, Will set it at 42lbs as well and give it a try. Anything to get this car going!

Perhaps I need to have the injectors rebuilt? There is a clattering from the rear injectors at idle when first started. Once warmed up the sound goes away. Will update next time I fool with the car. Thanks a bunch!