Signs of a bad lambda sensor?

23rd May 2011, 20:22

As title says, what are the signs of a faulty lambda sensor?

23rd May 2011, 20:25

over fuelling i think is one

23rd May 2011, 20:32

I've got over-fueling, flat spots when I put my foot down, and loss of power.
I've been getting shit MPG before but it's only just started to have flat spots and even more loss of power.
Could this be lambda related?

23rd May 2011, 20:37

it could be as it willl be giving false reading is its broken
change it and see what happens ifs still a problem then you know its something else

23rd May 2011, 20:41

I'm hoping it's just the lambda and nothing serious as I've just had a large bill to pay for a refurbished axle to be put on

Before it used to eat a lot of fuel, so that could've been where it was on it's last dying days, and now it's running real bad it could've finally died.
It sounds quite cool though as it pops like 2 or 3 times when down-revving from just 3k revs haha, but yeah in all seriousness I'll have a look

23rd May 2011, 21:15

sorry for slight spam but what would the flat spots be. like dyin a bit throught the revs asd mine does it also and EML says fuel injection fault.

what would be a way of testing which lambda is up the left?

23rd May 2011, 21:37

Poor cold starting as a lambda sensor has its own heating element,you can tell if your car is overfueling by taking the lambda sensor out.Then check the tip if its a black sooty colour then your overfueling it should be a white chalky colour.

Steve.

23rd May 2011, 23:02

Quote:

Originally Posted by tarzan

sorry for slight spam but what would the flat spots be. like dyin a bit throught the revs asd mine does it also and EML says fuel injection fault.

what would be a way of testing which lambda is up the left?

It just refuses to register that I've put my foot down for a second or two, then it eventually registers and kicks in, and as it down-revs like if I shift down a gear, it just pops like fuck a few times.

My EML was on originally, but I took it to a garage and he said that no error code was coming up so it could've just been a misfire or it needs a good service as it could be the sparkplugs.

Quote:

Originally Posted by stevo67

Poor cold starting as a lambda sensor has its own heating element,you can tell if your car is overfueling by taking the lambda sensor out.Then check the tip if its a black sooty colour then your overfueling it should be a white chalky colour.

Steve.

I'll have a look at the tip of the lambda tomorrow mate, cheers

30th May 2011, 17:35

I'm confused. Which lambda sensor r we talking about here? The one on the exhaust/near cat? or the one under the bonnet? I'm getting flat spots aswell now :/

30th May 2011, 21:13

Quote:

Originally Posted by j_a_lyons

I'm confused. Which lambda sensor r we talking about here? The one on the exhaust/near cat? or the one under the bonnet? I'm getting flat spots aswell now :/

Alright mate, I was on about my lambda on the manifold.
I had a garage check it all out and they first changed my spark plugs and it was all back to normal again with no more flat spots so they didn't check anything else, but I'm still getting shit MPG so I think the lambda's still in need of a replacement.

30th May 2011, 21:19

When was the last time your saxo had a service mate?ie fuel filter air filter.

Steve.

30th May 2011, 23:29

Had it serviced not long ago with very good oil and ngk spart plugs. Got a raceland with a green filter. I'm guessing it's the lambda sensor next to the manifold that needs changing. Can this affect performance and cause flat spots? R they easy to change? They look like theyre welded to the exhaust on a pic i saw lol.

30th May 2011, 23:48

Why not try cleaning the lambda's before replacing? Heres a guide I found on a different forum:

Quote:

O2 (lambda) sensors only work when they're hot and give a voltage between 0v and 1v. The main problem with them, I find, is that when they're a bit coked up they react to the heat of the exhaust gases slower and slower. This, I thought, corresponded very well to the low rate of recovery when the idle dipped down and returned to normal. You really want your O2 sensor to work 'fast'.

**Pictures here: http://s478.photobucket.com/albums/rr14 ... 0Cleaning/

What to do: either remove the sensor completely from the car and hold it lightly in a vice, or find something heat-proof ready to put it down onto under the bonnet; I used my soldering mat. Then heat the working part of the sensor with a gas blowtorch until it glows red hot. Play the flame into the holes in the sensor and all the built up carbon will turn to grey ash which can be wiped and blown away. Do this for a good few minutes until all the gunge has gone. I promise this will not hurt your sensor and when you've finished it'll work as good as new.

If you want to see the voltage shift yourself, before and after, wire up a multimeter to the + and - wires from the sensor beforehand (I can't remember which is which because I haven't bothered testing the voltage on one of these for a few years as I already know it works, but the info's available online). Play the blowtorch flame on the sensor and watch the voltage crawl up to 1v. Remove the flame and the voltage will gradually drop back down to around zero. After you've given the sensor a good clean with the torch watch the voltage again under heat - it will move much quicker, and when the heat's removed it will drop immediately.

After reinstalling the O2 sensor I took the car out and there was a huge difference in the idling. There was no drop to 500rpm when the clutch was dipped and slow-speed driving was much smoother. The idle sat at ~730rpm.

You can also use contact cleaner once you've cleaned all the shit off with a blow torch to get the rest off, but it may help before buying a new sensor.

31st May 2011, 01:47

Quote:

Originally Posted by stevo67

When was the last time your saxo had a service mate?ie fuel filter air filter.

Steve.

Not sure if you're talking to me or the other kiddy, but mine was serviced about 7k ago.

31st May 2011, 01:47

Quote:

Originally Posted by AL3X_

Why not try cleaning the lambda's before replacing? Heres a guide I found on a different forum:

You can also use contact cleaner once you've cleaned all the shit off with a blow torch to get the rest off, but it may help before buying a new sensor.

Cheers for that man, will give it a go