denso plugs are shit. used them on my alfa and the car was notably slower than the dirty ngks.

 

Are you using these Lou? How do you find them?
Cheaper than the Denso's on Sparkplugs.co.uk as well

 

Pie,

Could you post this in Forced Induction too. There was a big thread on this a few weeks back, and a lot of people will be interested to hear this.

MB

 

Good idea Mark - as they concluded that the Denso were only susceptible to damage in FI applications.

 

I have Denso IK24's in at the moment, but have a set of these in the garage. Will probably change them out next time.

They are just 1 step cooler iridium version's of the oem plugs. the gaps should be right and don't have a tendancy to fail. AE & Kelk have those plugs fitted I think.

The ones Amuse posted are the racing plugs definatly better but considerably more expensive and difficult to obtain. Probably only worth getting if your heavily modified.

 

Guys I'll update this thread after lunch, going to get some snaps of the plug damage, then I'll cross post a link in UTH

Not the first time a Denso has come a croper in an S, but usually it's missing electrodes

 

Aeons ago I used to have a Gilera 50 motorcycle that did that to all spark plugs, except NGK!

(I think the timing was a tad advanced - it was absurdly fast!)

 

Dropped tips on Iridium plugs are caused my ill informed people trying to gap the plugs - the tips are delicate, so if you catch them at all while gapping, they tend to fracture then fall off later.

Damage to the ceramic is potentially more worrying. Rarely a manufacturing fault. Normally means that either the ceramic was damaged during or before installation (eg. some clod dropped the plug on it). Or there's been some very abnormal combusion in that cylinder. It's actually possible that the ceramic damage happened after the start of your symptoms - it could be damage done by the rough running rather than the original cause of the rough running.

If it were my engine, I'd want to check it out a bit rather than just slapping different plugs in.

-Brian.

 

Brian,

You would be able to confirm if it was a running fault by comparing the condition and physical appearance of the 4 plug head / tips in this case.

MB