Does O2 sensor need changing?

[stevie_b]

For those who don't know, Nic is currently doing a group buy on O2 sensors (and a few other things) . I didn't want to spam that thread, so I'm starting a new one here.

 

Am I correct in thinking that my '93 NA requires 2 of these? How do I know if they should be (or need to be) replaced? If my car needs 2 of them, that works out quite pricey if they don't need changing!

 

I drive like a grandad, with occasional bursts of spirited driving. I get about 25mpg, which is 50% motorway and 50% town driving. I can't see new O2 sensors making much improvement on that.

 

Same question for fuel filters (also in Nic's group buy). How do I know if it needs changing?

[Markie]

30,000 miles for the O2 sensor I think it is. Could be wrong though..

[Ian C]

Your car will fail the MOT test for emissions if your O2 sensors need cleaning/replacing. It'll run too rich on idle. Your mileage will drop as well, quite significantly, as closed loop control under cruise will be too rich. Yes, an NA needs two sensors. If you experience problems, clean both and if that doesn't work, replace both. It'd cost more in fuel to try and diagnose which one was faulty But don't replace them until you have to - I see no point in swapping out perfectly functional components.

 

-Ian

[n00b]

Sorry really newbie question where are they located on the N/A? and also whats the best way to clean them...

 

Im thinking of just replacing them but i would like to know for future

 

Thanks

 

n00b

[milocoon]

My TT has done over 65000 on original sensors, flew through the MOT with Lambda bang in the middle of the test range. My mpg seems to worsen when its colder but on a motorway run its okay 125 miles from a 1/4 of a tank.

 

[JohnA]

...on a motorway run its okay 125 miles from a 1/4 of a tank.

How do you know it's a 1/4 of a tank?

Surely you don't trust the fuel gauge that much:Pling:

 

You don't really believe that you get 4x125=500 miles out of a tank, do you?

[Gamer]

Sorry really newbie question where are they located on the N/A? and also whats the best way to clean them...

 

Im thinking of just replacing them but i would like to know for future

 

Thanks

 

n00b

 

 

I have heard that Lemon Juice is good to clean it with....

[milocoon]

I did achieve 125 miles on a motorway at 80 mph and the gauge started full and showed 3/4 afterwards. I know this sounds good but the throttle hardly changed as the motorway was busy. I have also had as little as 250 miles and put £50 worth of super-unleaded in BTW !

[stevie_b]

I did achieve 125 miles on a motorway at 80 mph and the gauge started full and showed 3/4 afterwards. I know this sounds good but the throttle hardly changed as the motorway was busy. I have also had as little as 250 miles and put £50 worth of super-unleaded in BTW !

 

I think what JohnA means, is that the fuel gauge won't move much for the first 50 ish miles. The gauge drops faster as the fuel level drops, i.e. it's not linear. The gauge should only be used as a rough guide. You can't use it to estimate how many miles you've travelled for a given drop in the fuel needle.

 

Hope that helps.