Thanks again DonB. I've cleaned the Maf a couple of times using a contact cleaner which seems to work well and has been recommended. Everything else on the throttle body is good and tight and the spring seems to be strong requiring quite a bit of effort to move by hand. On occasion if the niggle has happened when I have been driving the check engine light has come on. I'm still toying with the idea that it may well be the O2 sensor as the fault only seems to occur once the engine has reached temperature.(working on the ecu only taking a read when the temp is up at the 250 ish mark) Also the other day when it happened I was stood at the rear of the car messing with a new aerial and you could smell the difference in the exhaust, like the old cars with the choke on.
I may well flip a coin to see which one to change first and see if the problem goes away.
Frenchfairplaydriver posted a video about the making of the 40 and after I'd watched it I surfed around Youtube and found a vlog by a guy called Hubnut who had bought a 40 (unseen) from Scotland and drove it the 320 miles home,brave. One of his issues was described almost exactly like mine and he had confirmed the O2 sensor to be at fault.
Either way, the cost is pretty much the same whichever I go for and it wouldn't be a bad thing to have to change both, although by the looks of it the Maf might be a tad easier.

 

Operating temperature for the O2 sensor is 300C/572F, and in order to allow it to reach this temperature, at startup the ECM runs in open-loop for awhile, ignoring the O2S output until certain conditions are met and it switches to closed-loop operation.

You can measure the voltages to and from the O2 sensor and compare them to correct operation per the voltages given in the manual, which you can download here:

AJ6 4.0L Engine Management System/OBDI Diagnostic Guide

I can't remember the exact symptoms I was diagnosing, but the original O2S on our '93 stopped switching voltages high and low and was just stuck at one voltage. Replacing it solved the problem. One thing I would recommend is that you spend a little more on an OE Bosch O2S with the correct electrical connector installed. The sensor is designed to draw fresh air through the spaces between the wires in the harness, and with the "universal" sensors that require you to attach the correct connector yourself, it is too easy to block these small passages and prevent the sensor from working correctly. In fact, the forums are full of accounts of owners who have had poor results with universal sensors.

Cheers,

Don

 

So I shall wait on verification of the O2 sensor brand/make and order one but before I do I shall get the multi-meter out and check as advised once again by DonB,thank you.

 

So a gap appeared in lifes busy schedule. The day was warm and slightly 'close' but with no wind so I had no excuse not to finish off the 'de-chroming' Previous posts shows the hows and whys and what used etc. Still think its worth stressing how much taking your time in preparation can save you loads of time in the long run and the end result is far more satisfying. It probably took me and hour and a quarter to mask up both front and rear trims. Three coats of etch primer and two to three coats of satin black.








You know when you've forgotten to do something but can't remember what it is? Well, once I'd packed everything away....the boot lid trim was staring at me...another day. Notice the aerial is a bit of an imposter. The original aerial came off in my hand. This one I found in the shed (Unopened and still in the original packaging) and is for the roof...I will sway out the mast, which just unscrews, for a short stubby one.All good.

 

So the O2 sensor arrived today but will have to wait a little longer before I can fit it, I'm sure there's a thread somewhere on here with some useful tips,as always though I shall take some photos and run through how I did it. The part ordered was DBC10744 and the seller very kindly informed me that it was indeed made by Bosch and was 100% the right part.Sweet.



DBC10744 for my 1993 XJ40 3.2S



Nice touch with the grease and interesting that there are small vents in the sensor end,not noticed that on other O2 sensors.



I will check the existing connectors before doing anything else,made the mistake of not checking before ,didn't end well.

 

So time has flown by once again. This will be my last update on this particular thread as the 40 now has a new home. I replaced the O2 and for the uninitiated,like myself, it wasn't a straightforward job. I may have missed a trick but whichever way I went at it it was awkward. After disconnecting the wires I managed with some help to undo the sensor from above using a number of extensions and an O2 sensor socket. A liberal soaking of penetrating spray is recommended before attempting. The heatshield around the exhaust pipe makes it difficult to get good purchase when tightening back up. If you remember the issue, it was that after about 5-10 of the engine warming up it would start to 'hunt' and would either cut out or clear itself. Working on the assumption that the O2 sensor was giving a faulty read when the ecu finally looked at it changing the sensor was a worthwhile starting point (looked to be the original one also) As it turned out the problem has not returned since the change. Happy days.
So she has gone to pastures new and hopefully the new owner will continue to enjoy her as I have done. Thanks to all who have helped me along our brief journey and I dare say I will be popping up again in the not to distant future but maybe not on this section for a while.


Never failed to raise a smile or turn a head.

 

twack,

Congratulations on a successful repair and on moving the car along to a new owner, who I hope will join us here if he or she is not already a member.

For others who are undertaking the task of replacing the O2S, the photos at the links below may help avoid some of the potential pitfalls (sorry the larger images are not currently working while Jag-Lovers is reportedly transferring files to a new server):

Oxygen O2 Lambda Sensor - Part 1 of 2
Oxygen O2 Lambda Sensor - Part 2 of 2

Cheers,

Don

 

Thanks Don B, as always you have been a true custodian of all that is helpful. Glad to know it wasn't just me being useless when it came to the awkwardness of the O2 sensor.
As of this Friday I will be Jagless as the S-type will be rehomed after a short flirtation with myself. I have my eye on a couple of candidates as it doesn't do to be without a Jaguar for any great length of time. I would say watch this space but I think it may well be another space...possibly an XJS as there is one up for grabs not to far from me and has been on the road up until the last few months...and its purple...till next time.Thanks to you all.

 

twack,

We'll anxiously await news of your next Jaguar acquisition, and hopefully it won't be too much of a "project."

Cheers,

Don

 

Excellent thread. Well done on saving this beautiful car. Inspirational.

 

Is the quote "The king is dead,long live the king" ? So I was Jagless for less than a week.
I listened to my head with regards the XJS and instead went for an XJR6 with a poorly gearbox. So I leave here with thanks and look forward to meeting up again on the X300 section....


XJR6 4.0 Supercharged,130k ish,poorly gearbox,dodgy wheel arch...Perfect!

 

That's a gorgeous XJR6, twack! Love the color!

I'll look forward to learning what you have to do to rectify the gearbox issues.

Cheers,

Don