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Thoric

Is my lambda sensor to blame?

19 posts in this topic

Hi all,

I'm a Ford Focus 2001 2.0l pertrol owner, and have been suffering from a worsening problem recently. I've been reading up and I'm beginning to think my lambda/oxygen sensor might be to blame - but I'd thought I'd ask everyone's opinion before I go out and buy a replacement! :lol:

The problem is that the engine has been stalling/rough idling. When I start the engine, it doesn't hold idle and just stalls immediately. I've learned to lightly press the accelerator to keep it at around 800 revs, and wait until it sorts itself out. This used to take no more than a few seconds, and all would be sweet for the rest of the day. But now I'm finding it takes anywhere between 10 seconds and over an hour to put itself right! I've learned to left-foot brake recently as I just cannot let myself take my right-foot off the accelerator for fear of a stalling engine.

The curious thing is what the engine does right when it sorts itself out: What it does is give a sudden burst of power, and then all is fine for the rest of the day! For example, I was once driving home, had been on the road about 25 minutes, and was cruising at 65 mph along the M11. Without moving my right-foot I suddenly got this burst of speed, taking me up to 70 in a few seconds! It then quick righted itself and I was able to drive normally from then on (no more left-foot braking at roundabouts etc.!)

So the clues I have are these:

  • Once the engine rights itself, it will be fine until it's completely cooled down (several hours later)
  • But the problem's not entirely temperature related, because I can drive for an hour and it won't necessarily of sorted itself out
  • It can sometimes be ok within seconds of starting the engine from cold, or not sort itself out all day
  • I was once told it might be a vacuum pipe to the inlet, but this hasn't fixed it
  • I've read that a faulty lambda sensor can cause a lean mix - which I presume can cause a cold engine to stall? Or a warm engine to rough idle?

Does anyone have any insightful advice or experience of these symptoms?

If it is a lambda sensor, any idea if it's the pre- or post-catalyst sensor? (I believe there are two, right?) (Can I inspect them to find out?)

Any advice will be greatly appreciated as I can't afford a Ford garage diagnosis, nor repair :(

Cheers all!

Thoric

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the lambda sensor only starts reading when the engine is at a certain temperature, not sure exactly what but its when it gets hot. Other things could be at fault, maybe the throttle position sensor? idle control valve? air flow meter maybe, a number of things. i think you should use a diagnostics machine to see if there is any faulty sensors. sorry couldnt be of more help

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if you can, get a 'live' data diagnostics done which should pinpoint your problem.

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Thanks FiestaMan and Mintalkin, I take it I need more advice from someone who can check out my engine with one of those OBD2 reader thingumajigs? I don't know anyone unfortunately, and I just know Ford will charge around £80 :angry:

Bit skint so I was hoping I'd diagnosed it correctly and could confidently fix it myself (least cost that way), but I wonder if I'll just have to face up to the fact I'm gonna need a professional. Bummer :(

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I'd be drawn to thinking its the idle control valve

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I'd be drawn to thinking its the idle control valve

OK, thank you for your input :)

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If you have breakdown cover get them out, they'll do you a code read free of charge to see why its cutting out. As VVG suggests its likely to be ICV

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If you have breakdown cover get them out, they'll do you a code read free of charge to see why its cutting out. As VVG suggests its likely to be ICV

That's a good idea - I do have cover.

So projecting forward. If this is the ICV, what am I looking at here? Dismantling the intake assembly? Cleaning and rebuilding, or new parts? I've not worked on an ICV before. Although I'm not averse to working on my car, this would be new to me. The most I've done before is replace the alternator, brake pads, wheel bearing etc. Is this possibly out of my depth?

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Usually taking it out and cleaning it up solves the problem for a while but it will probably return. AFAIK a new one isnt too pricey and many on the forums I visit do it themselves. I'm not sure on the how to as I'm more conversant with working on diesels.

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Usually taking it out and cleaning it up solves the problem for a while but it will probably return. AFAIK a new one isnt too pricey and many on the forums I visit do it themselves. I'm not sure on the how to as I'm more conversant with working on diesels.

Well - I've taken a look at a Ford Technical Information System CD and it would seem one needs to de-pressurise the fuel system!? Or am I taking too much off my engine!? :o You see, it says nothing about a Inlet Control Valve, but it does talk about an Intake Manifold, and throttle body. Are these the same things? I really am beginning to think I'm outta my depth :(

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Well - I've taken a look at a Ford Technical Information System CD and it would seem one needs to de-pressurise the fuel system!? Or am I taking too much off my engine!? :o You see, it says nothing about a Inlet Control Valve, but it does talk about an Intake Manifold, and throttle body. Are these the same things? I really am beginning to think I'm outta my depth :(

on a 2001 2l its not as big a job as you might think. the ICV is behind the inlet manifold so you have 2 options. 1. remove the inlet manifold etc or 2. remove the alternator.

personally i would just remove the alternator and go in that way, might be fiddly but it would save stripping half the engine to bits.

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on a 2001 2l its not as big a job as you might think. the ICV is behind the inlet manifold so you have 2 options. 1. remove the inlet manifold etc or 2. remove the alternator.

personally i would just remove the alternator and go in that way, might be fiddly but it would save stripping half the engine to bits.

Thanks for the advice stef123, I have replaced my alternator before so that's not too alien to me. I still don't know where this ICV is (other than that it's behind the inlet manifold), so I guess I need to do some more research. Anyone got any good links for websites with info (pics) showing things like this?

Oh yesah, will I need any replacement gaskets to do this? If so I'll need to get to a autospares shop before I strip the intake down because I'll have no transport options available to me once I do! :lol:

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Thanks for the advice stef123, I have replaced my alternator before so that's not too alien to me. I still don't know where this ICV is (other than that it's behind the inlet manifold), so I guess I need to do some more research. Anyone got any good links for websites with info (pics) showing things like this?

Oh yesah, will I need any replacement gaskets to do this? If so I'll need to get to a autospares shop before I strip the intake down because I'll have no transport options available to me once I do! :lol:

just pm'd you mate.

looking at pm's ive sent in the past, did i not help you out with replacing the ICV a while back? you sent me the ford data?

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just pm'd you mate.

looking at pm's ive sent in the past, did i not help you out with replacing the ICV a while back? you sent me the ford data?

Hi stef! yes, it's me again! I replaced the vacuum hose last time and the problem went away for a while, but as it's back I was hoping it was something else, like the lambda sensor. That might have been easier to replace! :P

I've just checked and I still have your original PMs, so thank you again for the info you sent me! I'll just have to bite the bullet and strip that ICV. It may not seem like a big deal to most of you hardened petrolheads, but I'm pretty new to something this involved and really hope I don't screw up my engine permanently! :lol:

Thanks to everyone who's advised me, if I'm on here on Monday then presume it all went well. If before, I'm in trouble! :lol: :D

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Hi stef! yes, it's me again! I replaced the vacuum hose last time and the problem went away for a while, but as it's back I was hoping it was something else, like the lambda sensor. That might have been easier to replace! :P

I've just checked and I still have your original PMs, so thank you again for the info you sent me! I'll just have to bite the bullet and strip that ICV. It may not seem like a big deal to most of you hardened petrolheads, but I'm pretty new to something this involved and really hope I don't screw up my engine permanently! :lol:

Thanks to everyone who's advised me, if I'm on here on Monday then presume it all went well. If before, I'm in trouble! :lol: :D

hope it goes well mate, its not a 'difficult' job its probably just more time consuming. where in the UK are you?

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hope it goes well mate, its not a 'difficult' job its probably just more time consuming.

That's reassuring, thanks. I'd better put the whole day aside...

where in the UK are you?

About 400 miles from Scotland :D

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:D Wahhay! Fantastic! Woohoo! :D

(childish moment over)

As you may have guessed - I've fixed it! And it's all thanks to you lot! Thank you for the advice and encouragement!

In the end, I cleaned out my ICV. To get to it I followed the instructions of a Haynes manual, as kindly provided by a member of this forum, and removed my alternator. In the end though you can just about get to it (on the 2.0 litre model this is) from the right hand side of the inlet manifold and from underneath. Takes a bit of reaching but it goes! I re-used the old seals (because I don't have access to a new one in a hurry) and it's running smooth now!

As a matter of interest, I borrowed something from work called Flux Off that's an evaporative grease remover. It took a hell of a lot of gunk out of it. Then I used long nosed pliers to move the seal up and down a few times to be sure it was free. Then another clean, then blasted it with compressed air (from another can) to dry it out. Put it all back together and, voila - one working engine!

...and yet I still don't know what the damn thing does! :o

Cheers again to everyone! Especially stef123!

FordOwnersClub rules! :lol:

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:D Wahhay! Fantastic! Woohoo! :D

(childish moment over)

As you may have guessed - I've fixed it! And it's all thanks to you lot! Thank you for the advice and encouragement!

In the end, I cleaned out my ICV. To get to it I followed the instructions of a Haynes manual, as kindly provided by a member of this forum, and removed my alternator. In the end though you can just about get to it (on the 2.0 litre model this is) from the right hand side of the inlet manifold and from underneath. Takes a bit of reaching but it goes! I re-used the old seals (because I don't have access to a new one in a hurry) and it's running smooth now!

As a matter of interest, I borrowed something from work called Flux Off that's an evaporative grease remover. It took a hell of a lot of gunk out of it. Then I used long nosed pliers to move the seal up and down a few times to be sure it was free. Then another clean, then blasted it with compressed air (from another can) to dry it out. Put it all back together and, voila - one working engine!

...and yet I still don't know what the damn thing does! :o

Cheers again to everyone! Especially stef123!

FordOwnersClub rules! :lol:

RESULT!! nice one mate. glad your all sorted again :) its a great feeling when something goes well - especially first time. take the rest of the night off with some beers :P

oh, the ICV basically controls the amount of air that goes into the intake as when the butterfly is closed on the throttle body little or no air would get passed. the air bypasses the butteryfly valve and goes via the ICV which can open or close accordingly. now if that makes any sense you will have the basic idea of how it works :)

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