Hey everyone, I've been the owner of a project 1992 V12 XJS for about a year. This is my first car where I've done any of the work really so I have what might be a newbie question.

When I got the car it had a check engine light on but it cleared and didn't come back once I changed the battery. The car had an occasional no start (starter cranks, but engine doesn't turn over) and a high and jumpy idle as well. I've synced the throttle bodies per the Palm book procedure, replaced all the rubber fuel lines under the hood, and had the fuel pressure regulators checked (they were good). I also checked the AAV by bringing the car to temperature and then blocking the air intake to it behind the air filter and I did not get a drop in RPM so I think the AAV is actually good but I have not had it off the car.
About a month ago I redid the fuel injection wiring harness (which was in awful shape, and the car sounds brand new with the new one). When doing that repair I also changed valve cover and intake gaskets, redid a lot of the other obviously faulty wiring on the top of the engine, and rerouted a good bit of it out of the V. Since then the check engine light has been on and won't clear. On the trip computer I have gotten both codes ff 36 and ff 44 at different times. I am not sure if I caused a problem with the wiring work or exposed one.

I know these are often o2 sensor or fuel delivery related codes and I am wondering if a faulty o2 sensor can also cause the high/jumpy idle and occasional no start issues?

Also, I've bene trying to search the forum but I have no clue what the o2 sensor looks like, where it is, or how to replace it. Assuming thats the repair I need to make any insight and/or pictures on that would be AWESOME.

Thanks

 

CHS,

Do you mean that the MIL won't extinguish after you've done a hard dump of the codes (disconnect battery for 30 mins) or that it goes but then comes back when you restart the car?

Paul

 

Thanks Paul. I didn't know you should disconnect the battery for so long. I've only disconnected it for 10-20 seconds when trying to clear the codes. What has happened is this usually works for a few minutes but after reconnecting the battery and starting the car the MIL comes back on anywhere from a few minutes to a day later.

 

CHS,

Try clearing the light and codes with a battery disconnect. Then check there are no codes showing via the trip computer. Then start the engine and run until the MIL is illuminated. Immediately turn off engine, turn on ignition and see what is the code that has illuminated the light. This way, we can start to see which is the code that is initially being set.

Cheers

Paul

 

FF36 is listed as B bank FI
Listed as :looks for uneven HO2S (heated oxygen sensor) feedback signal due to FI (fuel injector) flow or injector wiring fault on B bank (on left when sitting in car)

FF44 is A bank HO2S listed as: looks for correct HO2S (heated oxygen sensor)
B bank on right when sitting in car.
Heated oxygen sensor (also known as lambda sensor)








Lambda sensor is situated in the exhaust downpipe, one on each bank.

I had a similar fault code (FF34)
I assumed it could be faulty lambda sensor, before I fitted new lambda sensor I disconnected fuel injector plug from each injector on appropriate bank then reconnected each one.

In my case problem solved

 

Thanks again Paul. I was able to do this today and the initial code being set is the ff 36 code. I'll search the forum for a how to on changing the o2 sensors but would love any further insight as well. Thanks!

 

Still narrowing out issues here. I replaced both HO2 sensors but am still getting the ff 36 code. I've been told I should test the thermo-vacuum valve and I have a technical bulletin explaining how to do that. However, I'm not sure where that part is on the engine. Could anyone tell me or does anyone have a picture?

 

CHS,

Start by fully checking all the injector wiring. FF36 can be set if there is a problem in the fuel injector flow or wiring. That thermo switch sounds like the one that is mounted on the fuel rail EAC5086.

Good luck

Paul

 

The part number on the switch I am trying to locate is EBC 4599. I am hoping its not the fuel injector wiring because that would mean I built my harness wrong and I have no idea how I'll figure that out.

 

CHS,

There are 2 ebc4599 fitted on US cars. One is on the coolant rail, one is on the air injection system. As a matter of interest, who told you that ebc4599 will throw an FF36 code?

Paul

 

Thanks Paul, that's helpful. A local independent jaguar specialist mechanic put me on to the ebc4599 as a potential issue for the code. There is a TSB he gave me on the issue with instructions to check it, but I left it at work and don't have it in front of me to share more. I do recall that it listed it as something to checkout for a number of codes, not just ff 36.

 

CHS,

Try using Jaguar's own parts website which shows you the parts diagrams. You can also use the Search box on the left with the part number which can then take you to the appropriate pages. Remember not to put a gap between the letters and the numbers. See here for pre-facelift XJS:

Jaguar XJS parts | Jaguar Heritage Parts UK

Cheers

Paul

 

I would suggest checking that the injectors are plugged in correctly.

As I stated in my earlier post on my car it would start and run fine, but occasionally throw error code related to fuel injector flow.
It turned out one of my injectors was plugged in but not completed latched .
The injector plug has a spring clip that latches to lock the plug to the injector
It could be as simple as not connected fully. I cured my fault by unplugging each injector from wiring then replugging to ensure each injector plug is correctly latched on to the injector

 

Thanks, I am definitely doing this this weekend. Fingers crossed thats the problem.