Cleaned my throttle body and mass air flow sensor today, new air intake filter on order.
The car is 2002 XK8 - 148,000 km
Runs just fine, really fine, but I hear that older cars lose power due to contaminants etc... in the sensors.
I know there are symptoms, bad gas mileage etc... of which I have none, but should I change the sensors anyways?
I hear people say they regain lost power but thinking that my car seems to be fine, I'm not sure.
I want the best power obviously but don't want to waste money.
Any thoughts would be much appreciated!

 

I've moved your question from General Tech Help to XK8/XKR forum. This is the place to post technical questions about your model.

Graham

 

Others might chime in, but these O2 sensors are heavily monitored by the ECU as they are a major component in the control of emissions. Unless you have a code, I would leave the O2 sensors alone. Separately, on hard acceleration, the O2 sensors do not come into play (the feedback system is suspended). Replacing your AFM is likely the best bang for your buck in those blind parts replacement as it is the most upstream sensor and getting the right measurement there matters most. Depends on your threshold of pain relative to cost, I suppose.

Separately, you might gain some insight into the general condition of your engine operation by monitoring the fuel trims (both banks, short and long term). They are available over standard OBDII, so there is no need for a Jaguar-aware code reader. If you have nothing, start looking up cheap wireless ELM327 devices on eBay and Amazon (your phone is the display). High fuel trims (especially at idle, common on older cars) indicate air leaks and lowers the responsiveness of the engine. Fixing these leaks (o-rings, etc.) brings the trims down and an overall better driving experience. It is only when these trims reach 25% that a code is thrown, but the driving experience suffers with anything over, say, 5%.

Best of luck, keep us posted.

 

I would likely go with the "if it ain't broke, don't fix it" adage.
As fmertz says, the ECU goes open loop under hard acceleration, but I also believe that the curve it uses is derived from ECU learning during closed loop operation -n the long term fuel trims. So possibly if the O2 sensors are old, then the closed loop curve would be off, and then the calibration used for open loop also off.
I broke the heater on one of my upstream sensors when I tried to swap it into 200 cell cats I was fitting, I was too rough trying to break it loose. So for a while I had one new and one old upstream. I noticed that the old one read significantly leaner than the new one, and ended up replacing the other old one to get the pair to match again (which is why everyone recommends replacing both at the same time...duh) - i.e. as they get old, they read leaner than they should, and so the overall mixture is made richer by the ECU. How much richer is of course the question and I don't have a good estimate, since I don't have a good understanding of converting the upstream mA current readings to air fuel ratio.
Also they are a total pain to get loose without taking the cats off the car, lots of good tips in the forum but its no fun unless they are reasonably new and anti-seize was used, or you get lucky...