hi. i have a 1988 xjs and am having a difficult time with it. it starts and idles great but after about 5 minutes of driving it will not respond if i try to go over 1500 rpms it bogs down and then surges and bogs and so on.i have replaced the maf fuel filter and checked the fuel pressure whixh is fine.but it hasnt changed anything. i am not getting any codes or warning with the exception of power fluid level low. i cannot figure it out only thing left to do now is maybe the ecu but as i said its not kicking out any codes. does anyone have any ideas as to what the issue may be?

 

did you check your vacuum pressure? check it again on the PCM side of the fuel trim vacuum line. sounds like no fuel.

 

When she acts like that, put her neutral and rev her up. If in neutral still no go above 1500 rpm, fuel pump is weak, or fuel filter is clogged up.

 

the fuel pressure holds at 55 psi dont know if thats right but thats where it stays at idle and when it messes up.

 

no i havent check the vacuum pressure not even sure i know where the fuel trim vaccum line is but i will check all the vacuum lines for wear

 

There is no place that you check the fuel pressure that it should read 55psi.

Where are you measuring the fuel pressure? If you are measuring it before the regulator under the hood, it will be above 100psi. The correct place to measure it is on the left side after the fuel regulator and before the fuel rail. XJS does not have a schrader valve like some other cars to connect a gauge to so you literally have to cut the rubber line, insert a T and check it like that. It should read about 32psi to 33psi at that point. I bought a new hose and replaced it after I was finished re working my fuel system. I considered installing a schrader valve but did not want to add clamped connections.

 

Kirby Palm's Jaguar XJ-S Help Book
Over 700 pages of XJS help. IIRC the answer is in there, it is divided up into sections.

good luck
Pete

 

my bad i somehow typed an xjs i actually have a xj6 but it should still be the same correct?

 

Does engine temperature have anything to do with the symptom, or just driving time?

If temp sensitive you might also want to check the coolant temp sensor (behind left thermostat) as it plays a major role in cold fueling




Please clarify what you changed here.





Was the fuel filter clogged? Did you empty it into a clean container? If the contents was brown and cruddy, suspect a rusty fuel surge tank.

Agreed that we need to verify the fuel pressure situation, as mentioned. Regulated 55 psi would be too high. Unregulated 55 psi would be too low

Also, if you have a volt meter you can easily check the throttle position sensor. I can give details or the info is in Kirby's book.



Clarify, please



Are we sure we're talking about a 1988 XJS V12? The system didn't use trouble codes or have any form of on borad diagnostics.....so if you have a way of checking for trouble codes, we're talking about the wrong car!

Cheers
DD

 

NO! :-)

The '88 XJS and '88 XJ6 are entirely different beasts.

Re-post in the right section and you'll get some good answers.

Cheers
DD