1998 V70 Spark plugs look dirty, but are they normal?

brunocerous · Post by **brunocerous** » 06 Nov 2015, 08:01

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.

: Spark plug No. 4

On spark plug No. 3 (and No. 2, too, I think) there was also a light-colored, ashy residue visible on it.

: Spark plug No. 3 with some white-ish ashy residue

They look almost as dirty as the 2-year-old Denso plugs I pulled out of the car just two months ago. I recently also added STP Fuel Injector Cleaner), running 91 octane and then 89 octane in my last two fill-ups.

My question is: Is this level of soot normal?

Should I try a higher-quality fuel cleaner, like Lucas Oil? Use 93 octane?

Sommerfeldt · Post by **Sommerfeldt** » 06 Nov 2015, 08:33

I don't think I've seen plugs that dirty before... and certainly not after 2 months. Not normal.

I'm not sure about your model, but it's pretty clear that the 850s and early V70 do NOT enjoy the multi-electrode sparkplugs. You should probably try a properly gapped single electrode set, and make sure that the rest of the ignition parts are up to Stage 0-reqs.

- S

jcdillin · Post by **jcdillin** » 06 Nov 2015, 08:41

Ehh, I think you may have been sent the wrong thing if you ordered real volvo plugs.

https://www.fcpeuro.com/products/volvo- ... 90-8692071

I only use those or bosch copper electrode and properly gapped.

Post by **theWIFES_S70** » 06 Nov 2015, 08:45

Say it ain't so, FCP!

brunocerous · Post by **brunocerous** » 06 Nov 2015, 08:52

I see the difference! But that FCP link tells me, "This part does not fit your 1998 Volvo V70 Base."

Post by **cn90** » 06 Nov 2015, 08:53

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.

brunocerous · Post by **brunocerous** » 06 Nov 2015, 08:54

Sommerfeldt wrote:I don't think I've seen plugs that dirty before... and certainly not after 2 months. Not normal.

I'm not sure about your model, but it's pretty clear that the 850s and early V70 do NOT enjoy the multi-electrode sparkplugs. You should probably try a properly gapped single electrode set, and make sure that the rest of the ignition parts are up to Stage 0-reqs.

- S

Thank you. I might have to swing by the auto parts store to get replacements.

brunocerous · Post by **brunocerous** » 06 Nov 2015, 08:56

Here are the ones I had ordered.

https://www.fcpeuro.com/products/volvo- ... 60-8642660

Post by **rguzz** » 06 Nov 2015, 08:59

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...

Post by **cn90** » 06 Nov 2015, 09:07

Take the fuel injectors out and clean them to avoid leaky injectors.