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Spark plug issue?



Cliocup182!

ClioSport Club Member
  Clio 182 cup
I was changing out the spark plugs with new NGK items and stupidly connected the HT leads into the coil pack in the wrong order. When I started up the car, it idled roughly and then a pop sound came from the exhaust before I quickly switched off the engine. Total engine running time probably about 5 secs.

I then changed the order of the HT leads into the coil pack so they were in the correct order and restarted engine. No pops this time but engine sounded like it was running on 3 cylinders.

I then started to investigate, including removing each spark plug to check everything was okay. It turned out that the 2nd spark plug of the cylinder in from the drivers side was completely covered in black soot. So I tried to wipe this off with some kitchen roll and reinstalled (I would’ve used petrol or similar but didn’t have anything to hand at the time).

Started the car again and still sounds like it’s running on 3 cylinders, engine light flashes and then stays on. I used a different set of OEM HT leads the second time around so it can’t be them that’s at fault and I ensured the leads were properly seated on each of the plugs.

Do you think the spark plug with soot on it will be causing this issue now? It’s a brand new plug so I’m reluctant to change it out for a new one.

Would connecting the HT leads incorrectly in the first place cause any other issues that I might have overlooked?
 

Cliocup182!

ClioSport Club Member
  Clio 182 cup
Hmmm interesting. I’ll do that first then and see what happens. How do I narrow it down to which plug is faulty?
 

R3k1355

ClioSport Club Member
Well it's the sooty number 2 plug isn't it, the rest are fine?

Have you checked the gap on it to make sure it's not incorrect?
 

JamesBryan

ClioSport Club Member
  Titanium 182
Flashing EML is a fuel injector.

Probably just a coincidence that's it's gone at the same time as doing the plugs.

The light will be solid now because it's triggered an emissions fault. Too much unburnt fuel in the cat. That's where the black soot is from.
 

Cliocup182!

ClioSport Club Member
  Clio 182 cup
Flashing EML is a fuel injector.

Probably just a coincidence that's it's gone at the same time as doing the plugs.

The light will be solid now because it's triggered an emissions fault. Too much unburnt fuel in the cat. That's where the black soot is from.
Okay… so are you saying I definitely need to change the injectors or what next steps need to be taken?

Should I try to clean the sooty plug first and see if that resolves things?
 

JamesBryan

ClioSport Club Member
  Titanium 182
Okay… so are you saying I definitely need to change the injectors or what next steps need to be taken?

Should I try to clean the sooty plug first and see if that resolves things?

If the injector is bad then cleaning the spark plug won't fix it.

You could just replace one injector, but if they're all old you may as well do all four.
 

Touring_Rob

ClioSport Club Member
Lolololololololololol
Hmmm interesting. I’ll do that first then and see what happens. How do I narrow it down to which plug is faulty?

Come on mate, just put one of the old plugs back in, or move plug 2 to cylinder 3 and see if the fault travels - ie, does 3 now get sooty?

You can also unplug each injector one at a time to see which cylinder is missing, unplug the injector and if the engine stalls/runs worse that cylinder is fine.

I have just repaired an annoying misfire on mine, I replaced the plugs, coil pack and found the issue was just one plug lead which was intermitted depending on how you bent it.

The clio is wasted spark, so if the coil pack had failed you will be heavily missing on cylinder pairs (1&4, 2&3). An HT lead will miss on one cylinder only and given you have recently pulled these about I would suspect this however an injector can also be another source of a single cylinder miss. Again you can swap injector to another cylinder to verify.
 

Cliocup182!

ClioSport Club Member
  Clio 182 cup
Yeah. Normally always an injector on the one's I've done.

But it could be spark...
I guess it could be the injector but since all I’ve been messing about with is the spark plugs/leads, then it should be them I’m guessing. But obviously I’m no expert!!
 
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Cliocup182!

ClioSport Club Member
  Clio 182 cup
Well it's the sooty number 2 plug isn't it, the rest are fine?

Have you checked the gap on it to make sure it's not incorrect?
Nope I haven’t checked the gap. Is this something you should be doing with brand new plugs as a best practice?
 

Touring_Rob

ClioSport Club Member
You can test the resistance of the HT leads, mine were all in the 5-15k ohm range, however no.2 when twisted just a little went to around 100k.

I would progress by unplugging no.2 injector while the engine is running and seeing what effect that had on the idle (same or worse).

That will confirm which cylinder is misfiring. I would then swap no.2 injector with no.3 and see cylinder 2 stops misfiring, moving the misfire to cylinder 3. You can do all of that with the inlet on and it will tell you if it is a fuel injector problem or an ignition problem.

When the inlet is next off its also worth doing a compression test just for your peace of mind. I highly doubt its the case here but low compression can also cause a single cylinder miss.
 

Cliocup182!

ClioSport Club Member
  Clio 182 cup
Update… so I splashed out on a new spark plug and stuck that into cylinder 2 (from drivers side). Made no difference. So I unplugged the injector for the same cylinder and no change. Unplugged the other injectors and a definite change in engine note.

Sooo… now it’s a case of replacing all 4 since they’ve never been replaced and I might as well do them all.

Does anyone have any recommendations as to where will be the best place to get x4 new genuine injectors?
 

MRBILLYUK

ClioSport Club Member
  FF Jeden Osiem Dwa
Update… so I splashed out on a new spark plug and stuck that into cylinder 2 (from drivers side). Made no difference. So I unplugged the injector for the same cylinder and no change. Unplugged the other injectors and a definite change in engine note.

Sooo… now it’s a case of replacing all 4 since they’ve never been replaced and I might as well do them all.

Does anyone have any recommendations as to where will be the best place to get x4 new genuine injectors?
Renparts. Genuine Magneti Marelli. You won't get em cheaper anywhere else atm.
https://www.ebay.co.uk/itm/284133172043#vi__app-cvip-panel
 

Cliocup182!

ClioSport Club Member
  Clio 182 cup
known people to trap a lead under the inlet manifold when refitting and toast the lead (me :ROFLMAO: ) but it seems you have already ruled that out?
Yeah that’s correct. I tried a spare set of good leads that I had and it ran exactly the same so I’m 99.9% sure it’s not the HT leads 👍🏻
 


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