2006 XC90 bent plug electrode leads to lost engine

conflicted · Post by **conflicted** » 25 Feb 2015, 15:38

Hi folks, first time poster, bear with me.
I have a 2006 XC90 2.5T, currently has 226,000 km (135,000 miles or thereabouts). Last week on a frigid morning, the car developed a misfire. My mechanic pulled all 5 plugs and one negative electrode was bent over, contacting the positive. He replaced the plugs and off I went...for another 20 miles and it happened again. Mechanic pulled the offending plug, straightened the electrode, added another washer, then scoped the cylinder (saw nothing awry, the scope head wouldn't bend around to see the valves) and off I went. Whatever caused the plug to get bent has damaged one of the valves or the cylinder (no leakdown test done as of yet). I have other stupid warning lights (ABS and CEL plus others) which concern me but aren't part of this post.
So here I am, costing out used engines and driving around with a 4/5 luxury Volvo. If I didn't like the car so much, I'd ditch it with prejudice.
My question: what on earth could have entered the cylinder and caused that damage? Carbon? One dealer suggested the car inhaled the PVC valve. Finding out costs thousands. New head? $4,000. This has been a bitter experience.

draser · Post by **draser** » 25 Feb 2015, 19:24

There would not be that much carbon at that mileage to cause that. It would be hard to say what had caused that w/out removing the head. It's possible that a shard of the turbo vane has entered the combustion chamber and bent the plug and valve, however there should be marks on top of that piston. Then again, it's only speculation. Not sure how you'd get the pcv valve in there though.

Post by **cn90** » 26 Feb 2015, 10:21

What brand name and model of spark plug?

conflicted · Post by **conflicted** » 26 Feb 2015, 15:32

cn90: the plugs that came out were OEM Volvo, not sure what went back in.

draser: not sure I buy the turbo vane theory BUT...as you say, it's all speculation. Supposing a turbo vane did break off...would that help explain a moaning whine that comes out from under the hood when I drive...it seems to match engine RPMs and I can hear it better 1500-2000 rpm than at higher speeds.
I know turbos spin at unbelievable speeds and I think a bent or missing vane would cause a destructive vibration.
Cheers

draser · Post by **draser** » 26 Feb 2015, 18:23

Not to mention it would have to pass through the intercooler, then again we're talking a tiny sliver that will make it through the intake valve opening which is a few millimeters. What about the first damaged plug, was the porcelain insulator in one piece? Hard to say. What I can say is I'd consider finding another mechanic. Can't just add an extra washer to the plug. I was going to ask about turbo making an unusual noise, but at this point a 4 cyl engine will sound different anyways.

conflicted · Post by **conflicted** » 27 Feb 2015, 14:52

Yeah, the porcelain insulator is intact.
I don't need another mechanical opinion on the health of the mill, the diagnosis for the engine isn't in doubt: it's punched, and I need a new one. By the way, a used engine with about 100,000 miles from a local Volvo dealer is CDN$5600 and a quote from a friend-of-a-friend Ford dealer is CDN$3300 but I have to fine tune that amount, eg: does it include the turbo and is the new timing belt installed.
I like this mechanic; he's come by his trade 'old school' (Weber carbs? Lucas electrics? He's forgotten more about cars than I would ever know) and helped nurse my old Camry through many a crisis. If an extra washer keeps the car rolling while I think about this mess, I'm good with that. Loyalty does exist.

schweg2 · Post by **schweg2** » 03 Mar 2015, 12:28

Funny this exact thing happened to my wife's XC90 last week.

Happened on a cold morning here also.. bent #3 Volvo spark plug ground(electrode) with part of the insulator missing also.I Found a piece of steel (size of an egg shaped BB) in cylinder that got into the valves and damaged the seats. I Have no idea where it came from...

I checked the throttle body, MAF, no missing screws..I don't know but I installed a used head and am back up running, everything seems to be fine now.
I did have to hone a few score marks in the cylinder and polish the dome of the piston.

This happened to me once before after a valve job on a Ford Ranger, it bent the plug I screwed another one in and never had another single issue with it again.

You didn't happen to have any hoses off the turbo, ect and dropped something in there??

conflicted · Post by **conflicted** » 03 Mar 2015, 13:23

Thanks schweg2. Knowing another owner has experienced this breakdown makes me feel a bit better!
I had the timing chain done at a Volvo dealer last autumn. That was the last serious mechanical work done under the hood. More recently, oil and filter when snows were installed.
The used head is interesting. Volvo quoted $2,000 for a new head and 19 hrs to swop it....gaskets, rags, etc extra. How long did it take you? The potential cylinder wall and piston crown damage are worrisome but not unexpected. Cheers.

schweg2 · Post by **schweg2** » 04 Mar 2015, 18:52

I paid $250 for the head, the gaskets and head bolts were around $200.
I heard the same at 20 hours, It's not bad a little tight around turbo with the angle gear being in the way. Probably like 6-8 hrs?? Idk I work on alot of Volvo's so I know them fairly well.

If your concerned about your either get a bore scope with mirrors or pull the intake like I did and look through the valves.

When my new plugs come I'll check the compression and see if it dropped for shits and giggles.

Let me know if you need anything.

Post by **cn90** » 04 Mar 2015, 20:19

I found a few interesting threads below:

http://www.justanswer.com/volvo/6ukrm-v ... -plug.html

If you do a google search "volvo spark plug bent electrode piston" and hit "Google Images", you will see quite a few threads on this subject!