Good Day all
I experienced the following symptoms yesterday after driving my car around 20 miles when it ran perfectly as normal - lots of power etc.
On the return journey, the following occurred once the engine warmed up;
Noticeable hesitation in accelertion
Revs dropped suddenly when I tried to accelerate causing it to slow down alarmingly
Then a gradual loss of power until virtually stopped - limped home after leaving the car for a few minutes with the engine off - fortunately, I was within a mile of my home and only just made it.
This morning started the first time and felt normal - but after some two minutes of running the problem returned
I heard popping from the exhaust
Eventually, the car now warmed up exhibits extreme power loss.
I WOULD APPRECIATE ANY CONSIDERED OPINIONS .
I am assuming cylinder and compression problems
Many thanks

 

H iRay,

I am assuming you did not get any warning lights - gearbox or check engine lights?
I doubt it is compression or cylinder issues for this problem.
It is more likely a problem somewhere in the intake manifold side of things that is upsetting the vacuum level, thus confusing the MAP and MAF sensor readings that then tell the engine computer how much fuel to send through the injectors to suit the atmospheric conditions.
You probably want to start with checking all the vacuum lines that come out of the the manifold to go to the brake servo, auxiliary vacuum pump (if your year had that fitted), PCV valve.
These lines and their joiners are often hard plastic and can develop splits and fractures, giving rise to leaks that then cause misfiring and poor running.

If the car starts normally when cold, then it is not likely spark plugs (although you are at 94K so if they haven't been done yet they are probably due), nor is it likely a coil (unless it is breaking down as it warms up).
At cold start the engine running on high idle, so it will tend to mask any leak until idle starts to drop down as engine warms up.

Start with looking for vacuum leaks first...they are a common source of issues.

Hint: you can use a can of engine starter fluid to spray directly onto various vacuum pipes to see if an area is sensitive (engine revs will pick up) is a vacuum sucking leak is present.

If you are getting a gearbox or engine malfunction light, the problem is more deep seated and you might need to read the error codes and post them on your thread so we can see what you might be dealing with.
Could be an O2 sensor malfunctioning or something similar.

 

I thank you so much for your reply and appraisal. In view of the fact that I recently had similar engine problems
that required another 'Knock Sensor' fitted and the symptoms were the same - loss of power and Kangerooing.
I would say you are spot on. I will lt you know how it all goes.
obliged to you Sir

 

The other zero cost things you can do yourself is to check that the various earthing points under the bonnet are good, corrosion free, clean contacts.

Numerous members have had weird issues that have ultimately traced back to bad earthing. Some of the earthing points have several lugs stacked under the earthing bolts.
Your Cyprus climate might not induce much corrosion but you are likely a salt air environment,, so connectors and lugs could develop some tainting and unwanted resistance.

So set aside an hour to locate, undo and clean with light sand paper the lugs and landings of the earthing points. (if there are several lugs under one bolt, note the order of the lug stacking as oddly enough it has been mentioned by others that it can seem to make a difference if the order is disturbed).
Here are the various earthing points according to the 2002 schematic (which should be compatible with your production year) to help you locate them.

No harm no foul, it might just solve a gremlin.

 

Thank you Mark for this extra information. It is certainly something to take into consideration and I will
take a look at some of these points (hope I can actually find them) looks like around 21 of them to check.
At least I will not be bored this Christmas.
I keep thinking of selling the vehicle, but I cannot find anything that I feel is worth swapping it out with, and anyway
who would pay what it is worth to me these days?
Basically, I love the car, it is powerful, comfortable, and well made. I have spent a lot of money on resprays and
even had all the wiring looms out and fitted an internet touch screen, cameras & Bluetooth phone system
+ navigational facilities. It does usually run so well I am really loathe to part company with it.
Anyway Sir, all the best to you over festive sason
Regards
Ray

 

Hi Mark
Just to say the car has been checked over and after running the computer diagnostics it points to the
fuel pump under the rear seat not working. checked the fuses - all okay. then got the seat out and applied
some power - zero - no pump action. So once we get this out and check the part Number will get a
replacement to see if this was the problem or just a part of it.
regards
ray

 

OK, fuel pump is C2S51805 for our 2.1 V6 model.
It is different from the pump for 2.5 and 3.0 V6 models.
It is a bit of fun to get out, so I would first double check that your relay R11 is OK and also F18 (both in the power distribution fuse box).
If you successfully applied a separate power source to the correct plug pins to the pump (pins 1 and 5, which are the Green/orange wire and the black wire from the harness) and had no pump motor activity, then the pump motor brushes and commutator must be worn and have a dead spot.
Watch removing the fuel lines from the pump assembly.....the white and red clips are likely fragile now, so can be fun to try and reuse.
Hopefully your new pump will come with them, but a second hand pump may not.

Good luck with the repair.
Merry Christmas to you and your family.

 

Mark,
Removed the old pump - not quite so easy as although there was an access hole under the rear seat it was too small to get at the pump itself for removal.
So a very careful enlargement proved necessary as did not fancy taking the tank off etc.
Took the number off the old pump and replaced it with the same - all is now running perfectly. I bent the cut metal back into position and sealed it with
plastic sealant and refitted the existing rubber insert so as not to get the smell of petrol into the cabin.
I do thank you for your invaluable assistance.
regards
Ray

 

Possibly the first time I've seen a hitch on an XJS; though I have a facelift, could I ask which brand / model hitch and bike rack you fitted? Any issues?
Thanks!

 

Possibly the first time I've seen a hitch on an XJS; though I have a facelift, could I ask which brand / model hitch and bike rack you fitted? Any issues?
Thanks!

 

Apologies - not quite sure how these posts for the XJS forum ended up here☹️