As some of you know my car fired a CEL not too long ago the problem was fixed by having the valve clearances adjusted. During the process of diagnostics the spark plugs were changed to denso VK22 iridium.

Last week I took my car to reading to visit a friend I noticed the car was running a little rough and thought I will check it out when I get back.

On the way back I went to my friends house in hemel hempstead the car began to run really rough it was juddering until the cel light started to flash, the flashing eventually stopped until finally the CEL came on. I pulled over on the A41 I was 5 miles away from my mates house I drove it carefully back and parked up. The car was left there so I borrowed my mates GT-R 33 to get home the drive home cost me probably 20 quids worth of fuel

The weekend came so I drove back up to my mates house to attempt to sort out the problem I firstly read the ECU fault code it read a mis-fire on cylinder 4.
Naturally the first thing I done was to take out my spark plug. After taking out the the coil pack I noticed quite a bit of oil just above the spark plug inside the sleeve the rest of the cylinders were clear from oil. When the plug was removed I noticed that the ceramic part of the spark plug had dropped down and covered the tip. The ceramic part worked loose i could move it up and down by shaking it.

I mate had some HKS super racing spark iridium plugs which I replaced the car was started and the rough Idle had disappeared the CEL was still on and has now been reset the car was driven back 30 miles with no problems.

Denso Iridium spark plugs are meant to be good spoon sports sell them rebranded. They are not cheap so I would expect them to be reliable. I spoke to the dealer who I bought them from and would not do anything for me.

The denso spark plugs have covered no more that 300 miles and have failed already I am highly disapointed

 

that is not good and thankfully the ceramic part had not broken up

i suspect the oil could possibly be the seal between the plug tube and the cam cover that has failed, or been damaged when the valve clearences were done (i do hope the dealer had fitted new ones when the cover was off?)

i think it is very poor of the dealer not to supply you with at least 1 new plug, it's hardly going to dent their profit margin

 

plugs were fitted by myself

 

personaly i avoid denso spark plugs, 1 to many horror stories for my liking.. I think you were lucky. :-)

 

[QUOTE=motogp1,Jul 5 2008, 04:03 PM] personaly i avoid denso spark plugs, 1 to many horror stories for my liking.. I think you were lucky.

 

I think the oil leak is caused by the spark plug not sparking correctly causing pressure
I willl runt the new plugs and see if the oil build up continues

 

what pressure


this was Ben's (Bibbs) cam cover when i stripped the engine. there was oil on his plugs

 

It's corona staining and harmless
Corona staining

The plug failure has been caused by over torquing the plug into the cylinder head. It distorts the metal body meaning that the insulation material stops clamping the insulator properly and it starts to work loose. The loosening allows the gas to plow past the insulation material and et-voila you lose compression and get a misfire.

Since you've had gas flow past the plug it makes the corona staining worse.

I'm Toyota's manager of Denso products for Petrol engines so I've a fair few contacts with them. I got Pie and Chips plug off him when he had exactly the same issue a few years ago (same symptom, plug in same condition). I returned the plug to Denso who investigated it and gave me a report back on it.

I got some posters off them describing corona staining and common failure modes of over/under torquing the plugs. They probably have them on the web somewhere

 

fluff

Shattered that cyber myth

 

Hmm, surely Denso aren't going to say it was them though are they?