I’m looking for technical help or recommendations on: Spark plug condition
I have been suffering from a very intermittent starting issue where when starting the engine it judders and stall. It then starts fine on the second push of the starter button. The issue occurs only quite rarely and there are no fault codes shown.
I decided to take a look at the sparkplugs and found number 1 sparkplug to be in the condition as shown in the photo below. The other three spark plugs look fine.
I have replaced the offending spark plug but as yet do not know if it has made a difference to the starting issue. I would appreciate any ideas of how the sparkplug may have got in the condition it is in? When removing the coil pack there was no evidence of any moisture being present. The car has only done about 13K miles.
The car was bought secondhand. Whether the car has had a jet wash I don’t know. I wouldn’t see the point on a car that has only done 13K miles. The electrode looks much the same as the other plugs but the darkened area of the thread extends a little further than on the other plugs and perhaps looks a little wetter. The bore of the plug recess looked no different to the others but if there had been water in there it would have probably been boiled off by now.
Does look odd compared with the other three. Others look to be ok, nice and even burn and clean looking. TBH that offending plug looks like it’s something you’d take out of an old engine.
I was interested in an NC2 a couple years ago, absolutely spanking condition no rust underneath interior absolutely like new. I lifted the bonnet and it was wet through under there. I asked the question why is it wet (I knew really) they had fetched it out of it’s pre sales inspection/service for me to view. They had jet washed it to death under there.
For other reasons I didn’t buy it, but yes dealers do that. Not saying yours has been, but it’s the only thing I can suggest unless it these ND’s have a leak somewhere that’s gets to that particular plug.
This doesn’t sound very promising! I have replaced it with a spare plug that I had. I wonder if it could have been the cause of the random starting issue and a ticking noise (a bit like a tappet) that did not go away until the engine was fully warmed up. I did wonder if it was combustion product resulting from the plug being loose at some time. It did not feel overly tight when I removed it.
Just suggestions, I’m definitely not an expert.
New plug tightened to the correct torque could solve it. See how you go, let’s hope so and check it again a few miles on.
All suggestions appreciated guys. I thought that the plug bores were quite well sealed by the coil pack/plug connector but who knows. I just wondered if anyone had come across this before. I am not sure what the plug body is plated with (nickel?) and I would have thought that it would provide corrosion protection from water unless there was some electrolytic action going on.
That looks like damp has penetrated the spark plug cover. The plug firing has caused electrical tracking in this damp atmosphere, bit like lightning, which has caused the corrosion and build up of residue which in turn has led to more tracking and probably the resultant mis fire and other problems. Hopefully a nice new spark plug and a clean up of the plug cap connector will solve the problems.
My track record on fault diagnosis isn’t great, but I’d speculate that the plug has not been fully tightened in the past. That might account for the corrosion, extended discolouration of the threads, and even moisture, H2O being a product of combustion.
I see what you mean, the gap on the far right plug looks to be much smaller. I didn’t think to check the gaps as I had assumed the plugs had been in since new. I will recheck them when it stops raining!
Yep. You are correct. I remember now that I dropped one of the sparkplugs onto the floor from about 12 ins. The sparkplug on the right must have been it. I have reset the gap but I had already replaced the full set, so that sparkplug is now just one of the spares.
Yes, at the moment. However, the problem with starting was very intermittent and random. I would say on average roughly one in twenty starts. Time will tell!
From the condition of the plugs you showed us, I can see no reason why any problem would be random – unless the no.1 plug was only occasionally damp. For intermittent faults I would suspect a dodgy cable connection.
