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Spark Plug Fouling



Hi all,

Every few hundred miles spark plug number one (i think) nearest to the radiator gets fouled up with crap, bit oily. baked on sorta thing.

Easily cleaned and sorted but its happened twice now, any ideas?

Car sounds like a scooby firing on three.

Jay. :?

Oh yeah its got NGK platinums and new leads (not sure of make)
Fouling up.....

Dont wanna scare ya but mine started that malarkey and one day it stayed that way.....turned out to be rings :cry: :cry: :cry: well one ring to be exact :wink:

Good luck
Thanks for the reply.

What sort of cost do ya think that could be to replace the rings?
Pieces de ring

Well as is the norm, the rings are Renault only and were approx ?38 per cylinder. Then you got the labour to bear in mind and all the other bits, timing belt, head gasket etc etc

Good Luck
Hi Jay,
That sounds like what exactly happened to mine, mine started doing that on the same plug 2 weeks after i bought her, eventually even after cleaning the plug it would still only fire on 3 cylinders, i got the head taken off her to find that the liners where cracked :x the garage qouted me silly silly money for a rebuild (i was not in the club then) so it turned out to be cheaper to just buy a new engine from Renault, which i did 8)

Good luck and i hope its nothing serious.

My Quadra was doing that running on 3 plugs then i cleaned the plugs and it still was doing it, I too thought it was the liners or the rings
But one day decided to check the injector wires to find that the orange one was split and not connected properly, hence the fouled plug! so changed the wire and reconnected and it has been fine since!

?38 for a little bit of metal!!!!! Jeez.

ROB> was your plug covered in oil? or just carbon?

RODDY> How much was the engine?

My mate said it happened to him ages ago, the cars been stood for so long. He had it for 4 years and only covered 2000 miles.

Hes told me stick some redex in the fuel, clean the plug (again), and give it a good thrashing (something i havent done yet)

Gonna try this first but if theres oil gettin in there its gettin in there so some engine work needed.

Trouble is finding out whats the problem, checking wiring for injectors seems easiest.

Really wanna get this sorted cause the cars amazing and i hate seeing it not running right.

Cheers for the help

Jay. :(
Re: Fouling up.....

la21t said:
Dont wanna scare ya but mine started that malarkey and one day it stayed that way.....turned out to be rings :cry: :cry: :cry: well one ring to be exact :wink:

Good luck

one ring? did you file a divorce? :twisted: that can fix your car pretty fast :shock:
Fouling a plug.

Could be loads of things.

First stop is a compression test on all 4 cylinders. Start at number 1 (flywheel end) and end with number 4 (rad end).
Note the pressures, if you have cylinder (namely No 4) notably lower on compression you could have ring troubles.
What exactly does your plug look like? Colour, condition, wet or dry, shiny, glazed, damaged etc etc.

Does the car smoke at all? does it lose fluids?

So many questions lol.
If you're in the coventry area drop by for a cuppa and we'll have a sniff round it.
My engine price

Hi Jay,
Ma engine cost ?995 and thats including the vat, hopefully it wont come to that though mate, im sure the "vicar" will sort you out :lol:
Thanx for the info.

The plug if shiny, oily, but not damaged in anyway, maybe a little bit brown underneath the oil.

Dont think the car smokes, uses some oil every month or so but only a little. Waters ok.

Dave > How do you do a compression test?

Since i cleaned it this morning, ive put redex in and thrashed it up and down the A50 (always keeping to 70mph, honest :lol: )

Turned the boost up to 1 bar, its running great at the mo. So much power, hmmmm

Thanx all.


Dave > How do you do a compression test?

Er, with a compression tester? :lol:

Buy one, screw it into spark plug hole, disconnect main HT, spin it over a bit and take the reading on the gauge.

If one is low, put some oil down the bore the try again, if its back up to match the others then its rings.
I think the compression should be 10.5 bar in each cylinder with a max variation of +-.5

Oily black spark plug electrode is, unfortunately, a bad sign. Signifies worn rings/bores/stem seals.
Damm i sound thick.

Cheers dave, but could this happen on an engine with only 31k?

Cars been running great since i put that redex in (touch wood)
spark plugs

hi there

i had the same prob on my 21t plug 4. it turned out to be the rings so it turned out cheaper in the long run to buy a new engine it cost me from renault ?1000 all in.
good luck,
ady no 29

Yes, it could happen to a 31K engine, very little use can be bad too, one fouled oilway or siezed ring is all it takes....

Are you sure it's a genuine 31,000 miles?
Can you take pics and post them on here? If so i'd like to see a few pics of certain things thats all.....might help a little.
what pics of things you wanna see dave?

I know the cars history so im pretty sure its real.

So heres the story:

The car was originally brought by an arbic type bloke for his wife to go shopping in, cause she wanted a big car. She only went out in it once a week. It was not used often and then stored for years. Someone brought it and didnt keep it very long then swapped it my mate (sisters boyfriend) for his bent nova gte and ?50!!! (BARGAIN) cause the bloke was scared of the power and the fuel comsumption :lol: . My mates had it for 4 years buying it at 25k miles and only clocking another 5.5k on it, he has a works van so free diesel etc. So then i brought it, ive put another 900ish miles on it up to now, only had it 3.5 weeks (up to nearly 32k). So its gettin used at last.

Then my other mate tells me it used to be his boses car who used it every now and then. The same bloke who brought it originally.

Im the fourth owner of the car. AND THE LAST!!!!!!!! it aint goin anywhere!!!! I love it.

Only thing that puzzles me is the leather seats in the front are cracked and driver seat stitching has come apart in one area a bit leaving a gap. Usually only happening on high mileage cars, but dont know whether this also applies to leather.

Essay over.


my fingers are tired now.

What does it look like under the rocker cover?

Is there any writing on the top of the gearstick?

Is there and play in the drivers door hinges?

Are there any screws missing from the instrument panel surround?

Do the seatbelts or buttons look worn?

Does the drivers footwell carpet look worn?

The seats are prone to damage as you describe, but usually on higher mileage cars, although im not saying that its not possible.
dont know about rocker cover.

gearstick has been replaced with an alloy one.

Drivers door, well all the doors are very stiff.

No screws missing from the surround, cause ive had most of the dash apart recently fitting an alarm, imobiliser and custom made anit hijack system.

All the buttons work fine and dont look worn, apart from the sunroof button, the arrows have been rubbed off. The sunroof dont work.

Carpets are fine, no wear.
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