Cracked spark plugs

[ThePina]

Ok,

So I brought the car back to the garage today in regards to some pretty bad fuel economy (25mpg for motorway driving). Turns out my spark plugs were done, one was shattered and had a fair bit of fuel on top of it. Now these were changed about 5 months ago so its all a bit odd. It's worth mentioning that I still have an engine fault coming up (p0505) which my mechanic cannot trace the cause of and cannot get it to switch off.

Any thoughts on what may have caused this?

It's a year 2000, 1.6L s40.

[stevo48]

When you say one plug was shattered and had a fair bit of "fuel on top of it" what exactly do you mean?
If you mean fuel on the outside of the spark plug , I would have thought the only way that could have got there would be a leaking injector (unlikely) or the plug was/has worked itself loose allowing fuel to come past the threads of the plug.
If it is a plug that has worked itself loose this could also account for the shattered plug, if the plug has "blown" out whilst the engine was working it is possible the damage could have occured due to the plug bouncing around in the spark plug housing.
Which brand of spark plug have you been using, a lot of the members swear by using genuine volvo spark plugs only in their cars and i have found my car (1.6 xs) runs better with genuine plugs fitted.

[ThePina]

Hey Stevo,

That's exactly what I meant (as in fuel on the outside of the spark plug). Appears to have only been one affected.

How would I go about checking for damage? I've been using NGK plugs, had them fitted before I got on these forums and realised how much everyone loves the Volvo plugs. Is there actually much of a difference?

[Dog_Book]

Do a search

[stevo48]

Originally Posted by Dog_Book

Do a search

Yeah he/she could use the "search" facility at top but not everyone see's it.
Genuine Volvo spark plugs have been proven time and time again to be the most reliable and longest lasting spark plugs available for our cars, even the humble 1.6ltr can benefit from using oem plugs as I found out myself. I bought my car 5 years ago and discovered it had an intermittent misfire, I asked for advice on these forum and was advised to get genuine Volvo plugs, my problem was solved. Regards the high motorway fuel consumption, if you drive at or just under motorway speed limits you should get a return of around 30-34mpg, if however you put your foot down circa 85-90mph (not that we careful volvo drivers ever do) you can expect the mpg figures you have experienced.
Damage wise, not much you can do, any bits of spark plug that have fallen into the combustion chamber will either have melted, or got smashed to pulp or even have been blown out with the exhaust gases.

Edit; Where was your engine temperature guage pointing when the car is up to temperature, it should be steady at 3 oclock, I ask because an old or stuck thermostat will allow the engine to run cool and consequently the mpg will drop quite significantly.

[ThePina]

Thanks for info.

Been looking up on the thermostats a bit, mine sits nicely at 3 o'clock so I have a doubt that it's causing me trouble.

Thanks for the heads up anyways, looks like I'll be looking to get me some nice new volvo spark plugs.