Spark plug issue

SVO LOU · Post by **SVO LOU** » 23 Oct 2020, 19:11

Guys,
Have a question about my 01 xc70 with 208k that has been having weird spark plug issues the past couple of months and was wondering if anyone has any ideas...
Started a couple of months ago when the car started skipping so I checked the plugs and found #5 with the electrode actually touching the center conductor. Couldn't explain how it could happen so I changed that plug and the car ran great...For about a month. It then started skipping again and I found #4 with the electrode and center conductor/ceramic totally missing. Huh??? Used one of those small cameras that connects with your phone and looked inside and didn't see anything so I changed all 5 with new ones, priors only had about 20k on them (NGK), and car runs fine again.

Then today, started skipping again and this time I found #2 electrode looks like it's been hit, like the first one did a couple of months ago. Changed it and again it's running fine.
I can't make sense of it, even if the timing belt breaks nothing should ever come in contact with the spark plug, any one have any ideas?

For the most part the car runs fine with the exception of fault code ecm-9180 for the accel pedal, need to get one of those ECM pullers but that couldn't cause this...Totally stumped.

93SCMax · Post by **93SCMax** » 23 Oct 2020, 19:30

Are you sure you have the correct spark plugs? Could these be too long and the piston is actually hitting the spark plug?

I only use Volvo OEM spark plugs and have never had an issue with spark gap or electrode damage.

Post by **oragex** » 24 Oct 2020, 05:59

There are indeed sparks plugs with longer 'threaded' section for the 3.2 engine, however the ones in the picture appear to be the shorter ones. OP mentions the spark plug replaced lately looked like it had impact on the electrode. Could you upload a close up with this ? It's is hard to think there would be a foreign object inside the combustion chamber, rarely you may have a piece of valve chipped and falling inside. An engine compression should check for such event https://www.forddoctorsdts.com/uploads/ ... _64356.jpg You may also have the plastic tip of an injector falling, but usually it will stay inside the intake manifold
In the second picture, it looks more like a melted electrode. Same can also cause it to become very soft and bend, however given it stays upside down, I would expect the electrode to rather bend vertically, not horizontally. Only guesses. What could cause this ? First, as mentioned, use the right brand and type, not sure which one is right maybe this https://www.ipdusa.com/products/8273/10 ... 49-8642661
May want to look closely at all the wires going tothe ignition coils, including into the connectors, also the two screws 'ground' on top of the engine, the ground behind the engine. I'd make sure it has the correct Bosch ignition coils - no need to replace them if it doesn't misfire
If all checks fine, I'd think about the injectors. An uneven spray pattern can cause incomplete combustion and hot spots inside the cylinder. Removing them and sending for ultrasonic cleaning at a diesel shop is a good idea (never clean at home with solvents)

SVO LOU · Post by **SVO LOU** » 24 Oct 2020, 07:48

When I said the electrode was hit I only meant that by the way it looked, I don't actually see an impact mark on the electrode itself, sorry about that. The hot spot theory sounds possible, would there be any other symptoms to look for like O2 values? Thanks all

Post by **oragex** » 24 Oct 2020, 09:59

Possible incorrect air/fuel mixture to cause lean burning which will indeed overheat the combustion chamber. Not sure if the front O2 would do this,I would rather think it would cause rich mixture which would be the opposite of lean. There are several sensors used to adjust the mixture (and the timing advance). I would also make sure the coolant is correct and cooling fine. A code reader can give the exact coolant temperature (should be about 90-95C at idle) - temp gauge at 12 doesn't always tell the complete story, the engine head may still be overheating a bit.

Post by **kallekula** » 24 Oct 2020, 10:15

Go to Volvo and buy the correct plugs for your car and take it from there (if that wasn't the problem)

Post by **chrism** » 24 Oct 2020, 13:32

Is it a case of the lower electrode bending upward or the center electrode dropping downward?

Post by **E Showell** » 24 Oct 2020, 16:49

Use Volvo plugs.

SVO LOU · Post by **SVO LOU** » 25 Oct 2020, 20:20

Before all of the volvo plug recommendations I ordered Bosch ones.
Fingers crossed. Thanks all

Post by **SuperHerman** » 26 Oct 2020, 15:41

I am throwing this into the wind as a very long shot, but an explanation.

One of the banjo bolts has been known to fail and parts end up in the engine causing various levels of mayhem, including destroyed engines. There is an updated part which is a better design. If you do a search on the forum you will find the offending banjo bolt and discussions of its failure plus the updated part number.

It is possible a banjo bolt fragment is making its rounds inside your engine - then it is also possible something else is making its way between the valves as it opens and closes (something may have fallen in while service was being performed) and this item is breaking your spark plugs.[A relevant story - I recently found an aluminum starter bolt screw in my BMW after a dealer service, they are one time use and replaced. The tech must have left the bolt on the side of the valve cover and when I did some repairs on a sensor I heard a piece falling. Upon inspection I fished out the bolt. Had I not heard the noise and searched and found the bolt, it would have destroyed the engine. As Volvo don't have valve covers like BMW this is not an explanation, but if any work was performed to the intake such an event could happen.]

I would use your camera and remove each spark plug and look for evidence in the way of dents or scratches indicative of something hard in the combustion chambers. Thinking about it - the original broken fragment could be the culprit. You may have to rotate your engine by hand to get a good look. The fragment can move from cylinder to cylinder as the pistons go up and down and the valves open and close. Focus your inspection of dents/scratches where the spark plug tip sits.