P1336 misfire and hiccups

[Arfur Dent]

9 A.M ?

[Ozvtr]

took all the plugs out, all gaps were a little too wide so I regapped them, three were very clean, number 4 was a little sooty.

I also took the nearest (exhaust) cam cover off and had a look wondering if I could see any evidence of a sticky valve, nothing doing there but to really sure I would have to take the camshaft out.

Wait 'till you get home and put compression tester on it.
Listen to the exhaust for a "putt, putt" sound. See if a rag at the exhaust pipe gets sucked in and out.

As the car starts and runs albeit with a strong misfire and a smell of petrol I think the coil pack is failing on number 4 cylinder. But I have no way of testing it.

Don't get too fixated on the coil pack. Could also be a leaky injector. I'm not saying its not the coil pack, just keep an open mind. Just like the old coils, coil packs tend to "break down" under load and that's very hard to replicate. You could try "meggering" the coil pack or check the resistance of the coil primary and secondaries but that's a bit hit and miss.

I don't know if you know the principal of operation of the coil pack but just in case I'll give you a run down.
The coil pack only contains 2 coils. It runs on the "wasted spark" principal. It fires through 2 plugs at the same time. Plugs 1 and 4, 2 and 3. One cylinder is on the compression stroke, the other is on the exhaust stroke. Of course the only one that counts is on the compression stroke, the exhaust spark is just "wasted".
If you want to check the resistance of the primaries, pins 1 and 4, pins 2 and 4 of the electrical connector. The secondaries are across spark plugs 1 and 4, 2 and 3. Spark plug 1 is closest the gearbox.
If there was a problem with the coil pack internally, you would tend to have problems on two plugs. If you only have problems with one plug, that tends to be external to the coil pack. Like the plug (fowled, cracked porcelain, internal resistance) or the coil pack boot (brittle and arcing over).

I am also not happy at running it like this because of what it must be doing to the Cat.

Have you checked the fuel trims on the scan tool?
Can you view the voltage outputs from the O2 sensors? "upstream" should oscillate from just above 0 volts to just under 1 volt. "downstream" O2 should remain flat at just under 0.5 of a volt.
You shouldn't be able to smell fuel from the exhaust pipe if the cat is working, it should be burning it!

[Stanleysteamer]

Hi
This is fast becoming academic as the car is going into the garage as soon as I can get it there. The wife thinks it will be cheaper to get it fixed in France than in the UK. As she is paying I will not argue and she just might be right.
It definitely does smell of petrol as I said before but I am testing it with a cold engine so maybe the cat isn't up to temp to burn it off.
As I think I may have posted before, I cannot undo the connection from the loom to the coil pack so testing wires and stuff would be difficult and all I have is a normal cheapo multimeter.
But I am really grateful for all help and info you are giving me. I stupidly don't even have my Haynes manual for the C3 as it got left behind when we came over.
But my main concern at the moment is that the tow vehicle, my Discovery 2 TD5 is also playing up and without that I cannot even get it on the trailer and down the mountain to the garage, never mind all the way back up France and to home. And there is no Land Rover garage for miles.
thanks yet again.
Stan

[Stanleysteamer]

took all the plugs out, all gaps were a little too wide so I regapped them, three were very clean, number 4 was a little sooty.

I also took the nearest (exhaust) cam cover off and had a look wondering if I could see any evidence of a sticky valve, nothing doing there but to really sure I would have to take the camshaft out.

Wait 'till you get home and put compression tester on it.
Listen to the exhaust for a "putt, putt" sound. See if a rag at the exhaust pipe gets sucked in and out.

As the car starts and runs albeit with a strong misfire and a smell of petrol I think the coil pack is failing on number 4 cylinder. But I have no way of testing it.

Don't get too fixated on the coil pack. Could also be a leaky injector. I'm not saying its not the coil pack, just keep an open mind. Just like the old coils, coil packs tend to "break down" under load and that's very hard to replicate. You could try "meggering" the coil pack or check the resistance of the coil primary and secondaries but that's a bit hit and miss.

I don't know if you know the principal of operation of the coil pack but just in case I'll give you a run down.
The coil pack only contains 2 coils. It runs on the "wasted spark" principal. It fires through 2 plugs at the same time. Plugs 1 and 4, 2 and 3. One cylinder is on the compression stroke, the other is on the exhaust stroke. Of course the only one that counts is on the compression stroke, the exhaust spark is just "wasted".
If you want to check the resistance of the primaries, pins 1 and 4, pins 2 and 4 of the electrical connector. The secondaries are across spark plugs 1 and 4, 2 and 3. Spark plug 1 is closest the gearbox.
If there was a problem with the coil pack internally, you would tend to have problems on two plugs. If you only have problems with one plug, that tends to be external to the coil pack. Like the plug (fowled, cracked porcelain, internal resistance) or the coil pack boot (brittle and arcing over).

I am also not happy at running it like this because of what it must be doing to the Cat.

Have you checked the fuel trims on the scan tool?
Can you view the voltage outputs from the O2 sensors? "upstream" should oscillate from just above 0 volts to just under 1 volt. "downstream" O2 should remain flat at just under 0.5 of a volt.
You shouldn't be able to smell fuel from the exhaust pipe if the cat is working, it should be burning it!

I might just get the multimeter out and test the resistance of the plugs. I haven't known a plug give up the ghost in all my years of driving except when the porcelain insulation got cracked through clumsiness of taking out/putting back in. But there is always a first time. The wife agrees it wouldn't hurt to put a new set in anyway, but I am not holding my breath that this will cure the problem.
"Putt, putt" noise is deffo there.
Staying off it today as I have a back problem not helped by leaning under a bonnet!

[Stanleysteamer]

Hi all,
I have since last posted ordered a set of plugs and a new coil pack.
I will get the plugs tomorrow and fit them, but if after testing it is still missing I will then have the problem of fitting the new coil pack with the metal clip in the connector missing.
I assumed at first that I was supposed to push the metal c clip thing inwards to release pressure on some part of the connection to enable me to remove it. But this didn't seem to be working. So I thn thought that maybe I was supposed to pull on it instead, which I tried, it didn't seem to be moving so I put the tip of a flat screwdriver under it and levered a bit.
Too much as it transpired as the metal clip flew off hit something metal on the car, maybe the underside of the bonnet and has been impossible to see since.
So I am now stuck with separating an already stiff connection without the "help" of the metal clip.
Can anyone tell me how it is supposed to work? Please?
And does anyone have any ideas as to how I could still take it off without the clip? Pretty please?
You can imagine how stupid I feel. I am not usually so clumsy.

[Ozvtr]

The connector should just pull out now. The metal clip actually retains the connector onto the receptacle.

Yes, you push the metal clip inwards it releases the metal wire from the “ears” on either side of the plug, then the connector comes off.

[Stanleysteamer]

The connector should just pull out now. The metal clip actually retains the connector onto the receptacle.

Yes, you push the metal clip inwards it releases the metal wire from the “ears” on either side of the plug, then the connector comes off.

Hi Oz and others.
After changing the coil pack and the plugs it is back to running as normal.
I was able to get a coil pack for 62 euros and the plugs, Bosch, cost €35 so all in all OK. (Turned the mil off by erasing codes with my Foxwell.)
So I and the wife are very happy!
Nice to know a modern car has yet to beat me totally!
Thanks ever so much for all the time people have taken to help and advise.
All the best
Stan

[Ozvtr]

Thanks for getting back to us. It's very important to us to get feed back on members experiences. We can only build our knowledge base from the results of our members.
With limited resources, sometimes you have no choice but to bite the bullet and purchase the item that you think is the problem. Maybe right, maybe not. But you cant just sit there and mull over it forever!