P0135 Fault Code

[Mandrake]

hmmm, very interesting tomorrow morning i will monitor it again and listen carefully for the misfire. i noticed that when the accelerator pedel was pressed fast the motor would knock a wee bit (with a very small/quick stutter) and when i did this while recording the graphs for parameters the drop is noticed.

That does sound like an intermittent misfire under load alright. I've just been fighting with a similar problem although a lot more pronounced on my Xantia V6.

When you blip the throttle the combustion chamber pressures rise suddenly and dramatically, the higher the pressure the higher the voltage that is required for the spark to jump the constant size spark gap. Normally the measured spark voltage will go up dramatically when you load the engine or blip the throttle, and the spark will continue to fire.

If there is anything that is limiting the maximum available spark voltage then the cylinder will fire ok under light load/throttle but as soon as you demand real power from the engine or blip the throttle the voltage will be insufficient and the spark will not jump leading to a misfire.

In my case the problem was a puncture in one of the spark plug leads allowing an arc to the engine chassis. At low cylinder pressures only low voltage is required to fire the plug so the cylinder fires, at higher pressures the required voltage increases so the spark takes the easier route and jumps through the hole in the insulation to the chassis! Thus an insulation breakdown can limit the maximum available spark voltage.

Stuttering/stumbling/bogging when you blip the throttle is one symptom of a misfire under load, although there are other things that can cause that too.

In my case I was getting bogging when blipping the throttle, a noisier more raspy engine note, a loss of power, some stumbling/hesitation at low rpm and intermittent throttle lag. I was also getting a false lean reading from the oxygen sensor when accelerating.

As addo says it can be hard to diagnose an intermittent misfire, I've been poking and prodding at mine for a few months now but was looking everywhere else as I'd recently replaced the spark plug leads, plugs, coil pack etc... but it turned out to be that I'd damaged the new spark plug leads when replacing the original faulty leads.

One thing you could try if you have someone who could drive while you watch the Lexia is watch the upstream oxygen sensor voltage - when idling or cruising with light throttle you should see it rapidly alternate between <0.2v and >0.8v, this means that the mixture is correct. If you then accelerate hard with plenty of throttle you should see the reading swing to above 0.8v (rich mixture) and stay there. If it instead swings to below 0.2v (lean mixture) and stays there under hard acceleration then you definitely have a problem.

Either unburnt oxygen due to a misfire or a fueling problem that is limiting fueling leading to a lean mixture under load.

[addo]

Yes Patrick, I am in Sydney. You could try Reno-Reck for a used spare coil, otherwise get it posted over from the UK. My observations are that Berlingi do drop more coils than other Citroën cars of the same era; maybe they're hotter under the bonnet.

Edit: Darren or Ray at LCS Louth ("Louth Bikes") should be able to help as they have some Bougicord black plug units, twist their arm on postage though.

[patrickgledhill]

Cheers guys, this is very interesting and i will contact those parts guys for a used coil pack. i will monitor it under load on the computer and see how i go over the next couple of days.

thanks alot guys i will keep you posted!

[patrickgledhill]

Having to wait for a battery for my computer to arrive in the mail because it only ran on the power cord! so will be a few days. i do have to say that this van at times is loaded to the max, just the other day we had 500kg of solar batterys in the back, i am surprised at how well it handles! but thinking back driving it hard and when in low rpm (ie accelerating after changing gear) there are moments of hesitation/misfire. So i am very interested to monitor/record the data while driving.

cheers guys

[Mandrake]

If you have the ability to graph multiple parameters I'd suggest graphing engine rpm, throttle opening percentage, and oxygen sensor voltage.

What you're looking for is signs that the oxygen sensor is swinging to low voltage (lean) and flat lining there while you have >50% throttle at low rpm. At a light throttle it should alternate 2-3 times a second between high and low, and normally under heavy acceleration the oxygen reading should swing to high voltage. (Rich)

If you can also graph dwell times, ignition timing and injector opening times on the same graph all the better!

[patrickgledhill]

Allrighty, The battery for my laptop has arrived, so im off to do some tests now will post in about an hour.

[patrickgledhill]

Ok, so i have done heaps of recording and i have saved all the screen shots of the values onto flickr becasue i wasant sure how to add them on here.

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(can scroll through them using the older button at top of photo)

There are 7 photos in total, I can now do more measurements easily now that i have the battery for my laptop.

Cheers Guys

[addo]

Interesting that it suggests also wear to the TPS (if it's a cable throttle). Definitely coil issues at play, though.

[patrickgledhill]

Thanks Addo, that is interesting, the throttle setup is the same as on my 406 hdi where it has a cable running from the pedal to a small electrical unit under the hood. It does seem to drive fairly well, but you do notice a light misfire when accelerating from around 1500 rpm.

So the coil is definitely at fault, so i will try and get one organized tomorrow, what do you think of the chinese ones on ebay? will probably get one second hand though.

i will aslo change the plugs, NGK website recommends BKR6EZ but BKR6E are in at the moment are theses ok to use?

Thanks Again

[patrickgledhill]

Alrighty, i had ordered a coil from reno reck, 3-4 days and i should have it. cost $100 + $20 shipping. fingers crossed it does the job.
will let you know when I fit the new one.

Cheers

[patrickgledhill]

Wooho! Coil arrived yesterday and i fitted it in this morning. cleared the fault code and started it up. Straight away i noticed it idled much better and drives heaps smoother. also the car doesn't stutter when you blip the throttle just revs up nicely. I am very pleased with the result!

Thanks everyone for all your support, i cant imagine how much this would have cost at the dealer!!

again and again these forums are saving me money, awesome support

[Mandrake]

Excellent result Hopefully there has been no damage to the cat due to the misfire, if power and response seems back to normal you've probably dodged the bullet...

[patrickgledhill]

Yes well fingers crossed, i didnt even think about the cat but now i am even more glad it is fixed. cheers Mandrake

[patrickgledhill]

Well im a bit frustrated now, with the new coil in and it now running very nicely, the engine light came back on. so i plugged it back in and all that is there is the upstream o2 sensor fault. it took a few short drives for it to trigger that light. I have never managed to erase that o2 fault so i didn't think much of it. i have cleared the faults and the light is out but the fault is still there.(present when using lexia, but no fault when you go straight to SCANTOOL) why they are different i have no clue.

parameter measurements for the o2 sensor seem to look fine.

i will wiggle all the wire for the o2 sensor and see how that goes.

[Mandrake]

When you say parameter measurement for the o2 sensor look ok, what do you see ?

A good oxygen sensor, assuming yours is a narrow band zirconia type should show voltage swings from <0.2v to >0.8v multiple times per second, is that what you're seeing ?

The reading on a Lexia is only a rough guide as the number doesn't update fast enough to give a conclusive diagnosis, normally you'd need to look at the voltage waveform on a digital scope to see something approximating a square wave.

Although its quite a bit of reading you'll probably find the technical notes and diagnostic help sections of the following site very helpful in understanding how the sensor should be working and how to diagnose it:

http://www.lambdapower.co.uk/technotes/techindex.asp" onclick="window.open(this.href);return false;

Oxygen sensors typically don't fail completely, but start to misbehave in various ways, one of which is to become sluggish where the transitions between high and low occur too slowly, another way is it may get biased towards a lean or rich reading causing the ECU to compensate the mixture in the opposite direction. (eg if the sensor reads richer than it really is the ECU will make the mixture too lean)

Edit: just as I posted my link their website seems to have gone down. I'm sure it will be back up again soon though...