Lambda Sensor - some questions
 

In hope that someone can shed some light on this for me. I’ve got a problem with my car at the moment, without spending loads of money on various parts to try and solve the problem I’m trying to understand what each part does first.

Some questions about the Lambda Sensor ..

- Does removing the cats affects the way the lambda sensor works?

- Is it true that the Lambda sensor works up until you hit a certain revs (say 3000rpm)?

- Does the lambda sensor deteriorate over time or will it just go (stop working suddenly)?

- What symptoms can you expect if the lambda sensor starts to go?

- What is the average life of a standard Subaru (or is it Bosch) lambda sensor?

- can I replace the Sensor with a cheaper one (say Halfords or from buypartsby.co.uk) .. and will a 4 wire sensor be better than a 3 wire?

- Will a LambdaLink show up any problems with Lambda Sensor, and if so would it be worth buying the LambdaLink before a new Lambda Sensor?

:)

Problem I have is .. Hesitation!!! .. It can happen in any gear but only at low revs, once it hits 3000 (or near that) revs it breaks free and shoots off.

Car is a .. MY99 GL (Non-Turbo) - 54k miles
Mods .. H&S De-Cat Pipe 1&2, H&S Centre Section and H&S Afterburner BB

The problem started about 3 weeks ago, it first happened while cruising at around 45mph in 5th .. now it comes and goes in any gear at any time (hot or cold).

I’ve changed the plugs in the hope that it might be that but the hestation is still there. MAF sensor seems to be ok as its idling perfectly. The other thing is the HT Leads (or coils), but im checking the Lamdba Sensor first.

any help is appreciated .. cheers, Lee

Lets bump you back up Lee ;)

Simon :)

I would pull out and re-seat the HT leads as a quick check, and douse the outside with WD40 to ensure no water's getting into the system. Otherwise I suspect the coilpacks...

Good luck!
Richard

Thanks, I did the old WD40 on the HT leads when I changed the plugs last weekend, might take a look at some new ones as they've never been replaced since new (as far as I can tell with the FSSH receipts).


Simon cheers mate ;) :D


I would be gratefull to anyone who could reply to the questions as it would clear up a few things (mainly my understanding of how the sensor works).

cheers, Lee

anyone else?
 

Can any else help me out with my questions??

please .. look im on my knee's .. honest ;) :D

Top, cos I think My Lambda's on it's way out as well:mad:

* bump *

Dont know much about lambda sensors, but just replaced mine ,as i had hesitation, it never fixed it ,but all i know is the do last about 30,000 miles, think if they are on there way out ,you tend to use more fuel,i got aa replacment lambda sensor from http://www.cats-direct.com/oxygen_sensors.htm for about £40 as a genuine 1 was £200 lol, hope this helps

Thanks for the information and website, I cant really tell if its been using more fuel (think ive got used to seeing the fuel disappear at a rate of knots anyway ;)) but it looks like I'll be changing this next week and see if it does solve my problem.

Thanks again.

Regards, Lee

let us know mate if you get it sorted as there seems to be alot of people with hesitation probs

Lambda is used by the ecu to provide an AFR which allows the catalyst to most efficiently clean your exhaust gases (removing the cats doesn't change this fact :)). ECU does this by swinging the AFR backwards and forwards over Stoich (AFR 14.7:1).

But it *only* does this on light loads and up to a certain rev point. This is called closed-loop fuelling.

Once the load or revs go over a certain level (higher than 3k on a turbo Impreza), the ECU ignores the lambda sensor input and provides the fuelling that is in the maps. This is open-loop fuelling.

The lambda normally slowly under-reads as it gets older - this has the effect of causing over rich closed loop operation (requires more fuel to get the same voltage from the sensor), but has no effect on open loop running. It could well be the cause of your problems, but 3k rpm sounds a bit low for the switch between closed and open loop....

The lambdalink uses the stock lambda sensor, so if it is underreading so will the lambdalink. However, in closed loop you wont see anything different (ECU is busy throwing loads of fuel in the get the reading it wants from the lambda) - but when you switch to closed loop you should see your lambdalink suddenly appear to read very lean ;)

Also worth noting is that factory lambda sensors are narrow band - this basically means that they are not an accurate way of measuring AFR. All they are really good for is for providing a voltage swing as 14.7:1 is passed. They are also affected by high temps, under reading.

Lambdalink is a very good thing to have in car once you understand these limitations.

Best way to diagnose your problem is visit a friendly garage capable of checking exhaust emissions or AFR - if lambda is faulty, you're running pig-rich during closed loop. If particularly bad, you should be able to smell petrol when walking round the back of the car with engine running :D

Richard

Cheers for that dowser, its good to know how stuff works, i learn something new everytime i come on here

excellent! thanks dowser! Just what i wanted to hear, some informative answers :D

Im going to try and get the Lambda sensor tested over the weekend and depending on how it goes I'll probably replace it with one from buypartsby.co.uk or Halfords (whichever one is cheaper).

Thanks again. Lee

Just to give an update on the progress on this one ..

Took the car around to a specialist who concluded that my o2 sensor was completely DEAD! So im ordering one tomorrow and hopefully have it replaced by the end of the week :D