Spark Plug Wars – What’s Best for Your Volvo

"As are ALL spark plug threads. Brings out the crazy in people!"

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In theatres now. Please bring weapons.

The Problem

brunocerous »

Hi all,

I’m a longtime Volvo admirer and relatively new owner of a used ’98 V70 base model. Recently, I had some CEL blinking while driving to get my inspection done, turned around and got my scanner out. I was hoping for some insight.

After seeing a misfire code (P0304) in cylinder 4, I pulled out all the spark plugs (Volvo OEM via FCP Euro, replaced about two months ago) and saw some dark-colored residue. 

cn90 » 

Stay away from Denso plugs, they are known to break the tip off (Search Volvospeed).

– Switch to NGK Iridium BKR6EIX and you will never look back.
– Although Iridium plug is $7/each (Advance Auto Parts), Iridium easily lasts some 100K. The car will run very smoothly, you may see better fuel mileage.

The Volvo OEM plugs are overpriced.
Once you use the NGK Iridium, you don’t go back to copper or Volvo OEM plugs.

It might not be the spark plugs

 rguzz » 

Do a compression test +- leakdown when you change the plugs (again!). You seem to have a couple of wet plugs, from running rich, incomplete combustion or from oil, though looks a bit more like fouling from gas than oil. Do you use any or much oil? My 850t plugs don’t last terribly long because I have what I assume are leaky valve guide seals. Great compression, though. So I experiment with various grades of oil to try to keep consumption reasonable, which is working well enough. I’m a convert to 93 octane gas, finally, as well. Learning as I go along…
I’m going to go out on a limb and maintain that replacing the plugs will be a quick fix and that they will foul again. I like the leaky injector suggestion. How old are they? Is CTS a zillion miles old? Any evidence aside from the plug appearance that the car has been running rich? I suppose the non oem plugs you have in there could be entirely responsible for what you are seeing but I’m suspicious there is a yet to be an underlying issue. Admittedly, I’d probably do just what you are doing, but would maintain a nagging suspicion that there is still something awry. Good to get lucky, though!

Let’s back up a bit…

erikv11 »

Thread is a little all over the place …

– no, it is not good practice to use the turbo plugs in a non-turbo car. Not recommended at all, ever. The first few responses in this thread seem to have not noticed the car is NA.
– yes, the OEM plug for the NA is 3-prong
– the OEM plugs are about $5 each and proven to be superb over the last 20 years, how is that overpriced compared to a $7 iridium??? You will easily get 40k from the OEM, 3-prong plug.
– agreed, there is likely no plug issue at all here, the new plugs are just fine no need to replace.

Among other things the residue on those few plugs could be oil, due to leaky valve stem seals. Any smoke when revving after prolonged idle, or on startup? Injector idea is reasonable but you can’t clean them yourself.

And Then

 
and then

Spark Plug Wars

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