C5 - clicking with revs [solved]

[dnsey]

Unfortunately, perhaps, the noise picked up by your radio doesn't seem to correspond to the mystery noise. It sounds as though it's at ignition rate (6 x rpm), rather than engine speed like the ticking.

[Mandrake]

Unfortunately, perhaps, the noise picked up by your radio doesn't seem to correspond to the mystery noise. It sounds as though it's at ignition rate (6 x rpm), rather than engine speed like the ticking.

dnsey, ignition rate is not 6x rpm on a V6.

On a 4 stroke engine each cylinder only fires once every 2nd revolution of the crankshaft as there is intake, compression, power and exhaust strokes.. so on a 4 cylinder engine you get one power stroke and one spark per half revolution. Thus 2 sparks per revolution.

On an equal firing V6 there are 1.5 power strokes per half revolution (overlapping) and therefore 3 sparks per revolution not 6. On the earlier V6's like the ES9J4 cylinders spark together in pairs (wasted spark at the end of the exhaust stroke) meaning each individual cylinder sparks twice as often as it needs to but this does not affect the overall number of sparks per revolution in the engine, only where they spark, either way it is still 3 sparks per revolution. Later V6's like the ES9J4S in Ben's C5 don't use a wasted spark system, having 6 individual coils, so only one cylinder sparks at once but the spark rate is still 3 per revolution overall.

So on Ben's V6 there will be a spark occurring somewhere 3 times per revolution (thus the pickup from the ignition system overall will be 3 x rpm) but a given cylinder will only be firing once per every second revolution. So pickup from an individual cylinder ignition lead would only be 1/2 rpm.

Sorry to be a pedant.

Not that it really helps because even a normally functioning ignition system is going to be picked up on a radio held closely, so distinguishing between normally operating and a spark jumping where it shouldn't by listening to a radio is going to be very difficult, perhaps impossible without an identical car to compare it to...

[dnsey]

Of course, you are quite right - I stand corrected.
Nevertheless, if the mystery sound were the 'snick' of an HT arc outside the head, I would expect the radio to pick up a distinct corresponding 'crack'.

[Ben82]

Simon, you're such a fountain of knowledge

Hmm radio maybe out of the equation then.

I'm thinking next step to try would be using my laptop and webcam and lower the webcam into the area to see how far down the noise it coming from, maybe even can use it to look round gaps I cannot see from top down. Not sure if there's any other things to try really.

[Ben82]

I'm thinking next step to try would be using my laptop and webcam and lower the webcam into the area to see how far down the noise it coming from, maybe even can use it to look round gaps I cannot see from top down. Not sure if there's any other things to try really.

Tried this tonight, didn't really work very well, I don't think the webcam was picking up the ticking very well, and with it being dark even with the torch, I can not tell the way the camera is facing. So seems like I'll need to try it tomorrow during the day. If I can't get it to happen during the day, then it'll have to wait until I get back from the UK.

BTW it seems from that video he is able to rev the engine from the engine compartment? anyone know how to do this? (would be extremely handy for this issue if possible)

Think I've found the part that allows the pug people to do this (1920AK the pedal sensor), but it's position is under the electronics box on the C5, so is not the easiest thing to reach with my big fingers!

[Hell Razor5543]

The electrical noise could easily be coming from an HT area. However, that does not mean that you don't have an electrical problem. For example, if you look at the last few pages of the following link, you will see that Mandrake had problems with his V6 Xantia, and the problem appears to be faulty (and then damaged) HT leads. I wonder if you might be hearing the audible snapping of an HT lead shorting (when the conditions are right for it to be heard)?

http://www.frenchcarforum.co.uk/forum/v ... 57#p354157" onclick="window.open(this.href);return false;

[Ben82]

Hell Raor5543: the HT lead seems to be the most likely, however I have not really been able to see a break in the cable.. (I haven't gone so far as unplugging it all yet! maybe on a warmer day )

Did start to wonder if I could use the graphing stuff in lexia to see if I could see any differences in the readouts for the coils when the noise is happening and when it isn't, only issue is that when trying to save the log to get the graphs, lexia errors, and then closes... does it work fine for anyone else?
Or is there any other avenues people can think of for trying to narrow down where the clicking is coming from?

[Hell Razor5543]

I wonder if it could be worth looking under the bonnet with the engine running, but in the dark. If it is an HT arc, it might be possible to see it when it might not be possible under lighter conditions.

Be careful, and take a torch.

[Ben82]

I wonder if it could be worth looking under the bonnet with the engine running, but in the dark. If it is an HT arc, it might be possible to see it when it might not be possible under lighter conditions.

Be careful, and take a torch.

Done this a few times.. there's a few of the videos (not all) from it too in this thread.. one thing I did realise earlier when I looked under the bonnet (without the engine started) is that the engine cover does conceal some of the cables at the back, so next time it maybe worth taking the cover off to have a look to see if that reveals anything.

[Ben82]

Wonder whether doing this might help track it down, anyone tried this? (it doesn't work for Eric first, but then goes back to it later with it doing it properly).

[Ben82]

Tried spraying some water around the ht cable, didn't seem to really do much but the clicking doesn't seem to be coming from the visible ht cable, it seems like it maybe coming from the back of the engine fuse box area, but I think the only bit behind there is the sphere for the suspension?
Maybe I'll take my phone with a video into the dealers and see if they have any ideas. As I have none.

[Mandrake]

Don't know if its related Ben, but on recent occasions I've noticed a rapid clicking noise coming from somewhere in the vicinity of the battery or fuse box on my Xantia. Its audible with the bonnet shut while standing next to the front left wheel, and it seems to appear randomly, click rapidly (maybe 2-3 times a second) and eventually goes away, or goes away if I rev the engine up for a bit. I've also heard it happen once when the engine wasn't even running but the key was on but wasn't able to locate it. A bit baffled to be honest, it sounds like a relay or solenoid clicking.

[myglaren]

There is a widget in petrol cars that burns off fuel vapours from the tank that clicks. Could that be it?

[CitroJim]

There is a widget in petrol cars that burns off fuel vapours from the tank that clicks. Could that be it?

The charcoal canister purge valve...

Could well be. It's in the region of the fuse box on a V6 Xantia - just under the slam panel above the N/S headlight...

[Ben82]

Looks hopeful:

Looking for images of it, I found this So should help me identify it (wonder what happened to that Xsara!)

If it is that do you think it needs replacing? or is it more of another issue causing it to be active more often than it should?