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Citroen C3 1.4 2002 - Lean mixture - Fixed #

Posted by Shane Gray on August 23, 2014, 11:14 am

Year of Manufacture *: 2002
Engine Size and Code *: 1.4
( Optional ) ECU Type: sagem p2000
( Optional ) Scanner Used: dec ss 2

Hi,
I have this Citroën in at the moment with lean mixture . Oxygen sensor is fixed on 0.03 v. If you spray brake cleaner into inlet when running it switches to 0.9 v fast do oxygen sensor ok.

Sft is -25% lft is 22%, when revving up sft doesn't alter or o2 sensor. I have smoked it and found a few small leaks but after repairs it's still the same.
map reading is 1000kpa with ignition on and 300kpa at idle, vacuum is 20hg at idle. Compression test shows 180 psi at all cylinders. Injectors seem to spray evenly. Fuel pressure is 45psi at idle and holds with engine off. Had new t.belt so timing right.
Any help please? Dont no what to do next?
shane

Re: Citroën c3 lean mixture

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on August 23, 2014, 12:48 pm, in reply to "Citroën c3 lean mixture"
Lee Mackintosh

Just a thought,

is it possible you could change front and rear 02 sensors and see if anything improves.

I thought you added both fuel trims together for total fuel trim correction (but I may have completely got that mixed up) which means its running a -3 fuel trim at idle overal.

thanks
lee

Re: Citroën c3 lean mixture

Posted by shane gray <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3442' width='330' height='300' border=0 style='border:none;'> on August 23, 2014, 3:31 pm, in reply to "Re: Citroën c3 lean mixture"
Shane Gray

Lee,
short fuel trim is whats its doing now and long fuel trim is over a period of time. So in a way sft is same as o2 reading.
my be wrong but that's how I understand it.
shane

Re: Citroën c3 lean mixture

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on August 23, 2014, 4:23 pm, in reply to "Re: Citroën c3 lean mixture"
Lee Mackintosh

Shane,

I said I may have misunderstood it. Even so a minus figure means it subtracting fuel so if its requiring less fuel how is it running lean.

It maybe a slow response from 02 sensor causing the fault is what I am thinking as it uses this and the map sensor for fuelling/load requirements.

Unless it has a fuel delivery issue (poor injector flow quantity) I don't know what else it could be.

Re: Citroën c3 lean mixture

Posted by shane gray <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3442' width='330' height='300' border=0 style='border:none;'> on August 23, 2014, 10:23 pm, in reply to "Re: Citroën c3 lean mixture"
Shane Gray

Sorry lee,
its 25% stft and -22 lgft. Got it wrong way wrong.
Shane

Re: Citroën c3 lean mixture

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on August 23, 2014, 11:48 pm, in reply to "Re: Citroën c3 lean mixture"
Kevin Apps

Shane

Some bedtime reading for you.
http://www.obd-codes.com/faq/fuel-trims.php

Lots more if you search the web. including some video,s.

Kev.

Re: Citroën c3 lean mixture

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 10:14 am, in reply to "Re: Citroën c3 lean mixture"
Lee Mackintosh

I read that article and more but still fail to see how you have two different readings opposite scale.

I always believed that stft was immediate response from ecu according to what it see's from the 02 sensor and ltft was as it states longer period of correction.

So we have stft chucking buckets of fuel in (maximum corection) but ltft almost doing the exact opposite to its maximum correction. Can someone please explain this.

Adding fuel (stft +25) seems to me an air leak must exist but I'd expect ltft ro also be correcting in the same direction.

Can't you force a rich condition by disconnecting the coolant temp sensor and see how the 02 sensor reacts along with the fuel trim figures.

I still think its worth swapping front & rear 02 sensors to see if it alters fuelling.

Re: Citroën c3 lean mixture

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 10:49 am, in reply to "Re: Citroën c3 lean mixture"
Kevin Apps

Lee

Shane really needs to re-set the learnt value,s first.

Kev.

Re: Citroën c3 lean mixture

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 11:17 am, in reply to "Re: Citroën c3 lean mixture"
Lee Mackintosh

Kev,

I look at the data provided as the ecu doing its job and corrected the lean condition to a point but it is strange how they read opposite.

total fuel trim is +3 so seems fairly good. Stft is reset every cycle of the key whereas ltft is stored and this is where the ecu starts off again.

so in theory it will start up with a lean running condition until all learnt values are reset by clearing the fuel related data in eobd.

A negative ltft fuel trim will cause a lean condition though won't it? Which will then show up on the 02 sensor as its requested less fuel to be injected.

Re: Citroën c3 lean mixture

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 1:18 pm, in reply to "Citroën c3 lean mixture"
Kevin Apps

Lee
I will stick with my original statement Shane needs to clear the "learnt" value's.
Kev.

Re: Citroï¿½n c3 lean mixture

Posted by Jim Power <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3202' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 2:01 pm, in reply to "Re: Citroën c3 lean mixture"
James Power

Is it not possible that at the time when viewed,

ST 25% is attempting to return back the LT -22% to the target value of approx 0.

The fault may not be present under all conditions.

jim power

Re: Citroï¿½n c3 lean mixture

Posted by Shane gray <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3442' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 5:29 pm, in reply to "Re: Citroï¿½n c3 lean mixture"
Shane Gray

Lee,
I presented an air leak by removing vacuum hose and O2 and sft didn't move. I presented a rich condition by spraying brake cleaner into inlet and O2 shot up to 0.9v and sft moved to 5%, so that proves O2 is switching fast and is working, as soon as brake cleaner burnt off it shot back to lean condition.
Kev how do you reset learned values? How is resetting going to alter stft?
Shane

Re: Citroï¿½n c3 lean mixture

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 6:37 pm, in reply to "Re: Citroï¿½n c3 lean mixture"
Lee Mackintosh

Shane,

If you add a fuel source then the immediate response of stft should be go to a negative reading as its taking fuel a way not adding anymore and if you use propane in the air intake you'll see the long term also go negative because its trying to compensate for the rich 02 sensor and the stft reading.

I think a good example of this is a Corsa with an afm issue. You'll see a max reading of + 20% ltft because its adding fuel due to a slow response of the afm which the ecu believes it to be a lean condition and often sets a p0170 error code or an 02 sensor code.

I think you can resrt adaptions or try clearing emission related codes using eobd and then rerun the car to see what fuel trim figures are.

I only have a very basic understanding of this subject but had an issue with a Chevrolet Kalos which taught me a bit about fuel trims and the CAT's ability to store oxygen.

Re: Citroï¿½n c3 lean mixture

Posted by andrew pethig <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3731' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 7:18 pm, in reply to "Re: Citroï¿½n c3 lean mixture"

to clear fuel trim adapations/ learned values, you will need a scan tool with vehicle specific functions , adapations can not be cleared from EOBD2.

if there is no fault the fuel trims should sort them selves out after a fairly short time .

shane you havent said if there is a fault code to go with your lean condition.

you also said that creating a air leak the o2 sensor voltage did not move from 0.3v this is not fully lean 0.1 is . Edit you posted 0.03 so this is fully lean

Is it not posable you just have a bad o2 sensor ?

what does the rear 02 sensor do when you create a big air leak ?

pull off the brake servo hose and see what you get.

what does the rear o2 do when you add brake cleaner ?
if the rear 02 is a good sensor can you swop the front and rear to see what you get.

Re: Citroï¿½n c3 lean mixture

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 7:25 pm, in reply to "Re: Citroï¿½n c3 lean mixture"
Kevin Apps

Shane

Have your read the article in the link ? did you search out more article,s ?

If so you will know why your LONG term trim is where it is (-22 %).

You have not really posted the full story yet,we dont know why the car is in (mil on and you have code read it ?), what code(s) etc etc.

Most dealer tools have a re-set learnt value's function on most engine control unit's.
Kev.

Re: Citroï¿½n c3 lean mixture

Posted by Lee Mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 7:25 pm, in reply to "Re: Citroï¿½n c3 lean mixture"
Lee Mackintosh

With a +25 stft and a -22 ltft isn't that on its way to sorting its self out.

I still see that as a +3 overal fuel trim. Clearing all learnt values is the only way to reset memory of ltft.

Re: Citroën c3 lean mixture

Posted by shane gray <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3442' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 7:31 pm, in reply to "Re: Citroï¿½n c3 lean mixture"
Shane Gray

Kev,
it came in because it was cutting out and jerking in first and second. Fault code p0300 I think cylinder misfire and 02 sensor code liw voltage can't remember code.

Re: Citroën c3 lean mixture

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 7:39 pm, in reply to "Re: Citroën c3 lean mixture"
Kevin Apps

Shane

So what does that tell you ?

Have a think about it, i'm off out for a beer or two.

Kev.

ps. You still did not answer my question's about the article's !!!

Re: Citroï¿½n c3 lean mixture

Posted by Mark Carter <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on August 24, 2014, 7:48 pm, in reply to "Re: Citroën c3 lean mixture"
Mark Carter

Reset the trims and move on with the repair.

Modern cars, Its all wizardry and witchcraft

Re: Citroen lean mixture

Posted by Shane gray <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3442' width='330' height='300' border=0 style='border:none;'> on August 25, 2014, 8:51 am, in reply to "Re: Citroï¿½n c3 lean mixture"
Shane Gray

Kev,
Thanks yes I just read info.
On Tuesday I will reset learned values and go for test drive.
I will post fault code and live data reading.
Thanks enjoy bank holiday
Shane

Fixed #

Posted by Shane Gray on August 26, 2014, 10:49 am, in reply to "Re: Citroen lean mixture"
Edited by board administrator August 29, 2014, 2:12 pm

Morning,
Right ok by the looks of things the air leaks I fixed last week, which were injector O-rings and breather pipe made the fuel trims go to max 25% and lock out.
I reset learned values this morning and fuel trims and o2 sensor switch correctly.
Lesson learned RESET LEARNED VALUES!!!!!!!!
Thanks Kev
Shane
p.s I would assume clearing codes would reset values?

Re: Citroen lean mixture/FIXED

Posted by Lee Mackitntosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on August 26, 2014, 11:48 am, in reply to "Re: Citroen lean mixture/FIXED"
Lee Mackintosh

I thought by clearing the codes in eobd it reset the fuel trim learnt values as well.

thanks
lee

Re: Citroen lean mixture/FIXED

Posted by SHANE GRAY <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3442' width='330' height='300' border=0 style='border:none;'> on August 26, 2014, 1:46 pm, in reply to "Re: Citroen lean mixture/FIXED"
Shane Gray

Hi Lee,
So did I, but after reset the SFT went to 0 and LFT 0. Car runs nice.
One to remember! Wasted few hours on something simple!
Shane

Re: Citroen lean mixture/FIXED

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on August 26, 2014, 3:47 pm, in reply to "Re: Citroen lean mixture/FIXED"

Shane
"Wasted few hours on something simple!"
Yes so get on some training course's and they will pay for themselves many times over, and your customers will love you for it

Kev.

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