Misfire

[als_jordan]

Alright all,

My car has developed a misfire over the past week or so, its only at idle and off boost less than 2000rpm.. Still pulls fine on boost with no probs :nod:

Thought at first it was the coilpacks but thanks to LKDrifter for letting me borrow one i have now ruled that out (thanks Martin!) I replaced them one by one, and it made no difference...

So then i started more digging mainly around the SXOC and the Tech S14 forum.. It seemed that apart from coilpacks, plugs, CAS.. One of the main culprits was the Lambda or O2 Sensor...

I got out my consult software and plugged it in and went for a drive, O2 sensor gradually crept up to 30, before i left and then dropped to zero for most of the drive?? Then when i pulled in and sat it idling on the drive the o2 sensor started to creep up and up.. When it hit 60, the car started to misfire and idle roughly, looking at the consult output the timing was fluctuating quite significantly going from 10 to 30... (before this when idling the timing was pretty much spot of 15 degrees..)

This morning i decided to drive to work without the lambda sensor connected, and would you believe it no misfire when i got to work and left it idling for 5mins...

So reconnected the lambda on the drive home and then when i got home let it idle to it misfired, started a consult trace, then disconnected the lambda and the misfire went away. I reconnected it and it then came back... The Consult shows the timing gets much more unstable when the lambda is connected and it goes above 60, if i disconnect it the timing stabilises and the misfire goes away

So i now have a number of questions??

1. What should a Lambda sensor read, both on idle and whilst driving?
2. Is it true that a lambda sensor only works <2000rpm?
3. Could these symptoms actually be another problem and unplugging the lamba sensor is just masking other issues?
4. Is the lambda sensor easy to replace or could it be a *****? It goes through a lot of temp extremes...? (I have seen the links on here for the O2 sensor socket and where to get the cheap lambda sensors - cheers!)
5. What unit is the Lambda sensor measuring in Consult?


So what do people think? Have i got it right and need to get a new lambda sensor?

Thanks in advance, and sorry for the long post! :thumbs:
Als

 

[als_jordan]

so what do people think?

 

[Yakozan]

Not sure how a lambda works. But it definetly sounds like yours is fubared.

changing the lambda might be a bit tricky. There isn't alot of space and it's often pretty hard to remove. But if you have the right tools it shouldn't be too difficult. It should be possible without removing anything around it, but I haven't tried myself.

When I moved my lambda to my new downpipe I had the downpipe out. That little bugger needed quite some force to let go. I ended up using a huge wrench to get some leverage.

I think there is special lambda sockets you can get. That would make things easier.

 

[LK Drifter]

I've got a lamba socket mate, But be warned they can be a bugger to remove!

 

[Matt_S]

Bastard to get out most of the time!

http://en.wikipedia.org/wiki/Oxygen_sensor

 

[als_jordan]

great thats what i thought... thanks for the link i now understand i was right regarding <2000rpm and 'closed loop' mode...

Bastard to get out most of the time!

http://en.wikipedia.org/wiki/Oxygen_sensor

 

[als_jordan]

Thanks mate, I am hols now for a week or so, but when i am back do you think you might be able to give me a hand (and the lambda socket), I'll return the coilpack then as well if that's ok?

I'll order the sensor when i get back first....

I've got a lamba socket mate, But be warned they can be a bugger to remove!

 

[chriss85]

I was going to change mine aswell, so I'll watch this space.

 

[LK Drifter]

I can try mate, but I dont know how much luck we'll have as I broke mine taking it out. I had to remove the down pipe in the end.

 

[als_jordan]

mines in the elbow i think????

 

[Yakozan]

I can try mate, but I dont know how much luck we'll have as I broke mine taking it out. I had to remove the down pipe in the end.

the lambda sits in a big nut which can be removed. It was easier for me to remove the whole nut as the lambda just wouldn't let go.

I was pretty lucky though that my new downpipe required this nut.

 

[Matt_S]

Yeh theyre in the elbow. But theyre a fcuking mare to get out in the car!

Its sometime seasier to bite the bullet and remove the whole front pipe/dump pipe assembly and do it that way.

 

[als_jordan]

Just thought I would post an update, got a new lambda and it has sorted all of the misfire issues, now showing up in consult correctly as well!! FINALLY!
Hopefully i should start to see better mpg too...