Check wiring harness for melting and shorting. If all ok, check compression. You may have a burnt valve, I’m sorry to say.

 

Harness seems fine

 

I had a similar issue. Check my thread "Code misfire" I have now removed my cyl 2 injectors. When I disconnect the 4 others the engine run muck worse but on cyl 2 nothing happens. I will replace all 5 it expensive but it not fun to remover everything if another will be bad soon. the are 15 years old according to the manufacturer date. So if the have been running since the car was new, its time to change all.

But I was hoping for more replys before order if there are more things to consider.

 

If your already not getting a fire event, even when u unplug the injector you would not expect any change so that isnt a good tell. I will check compression first and if thats not the problem look into the injector a bit more

 

Ran a compression test, read 0, im ruined. RIP hank the tank

 

Before you give up on it, pull the intake manifold off of it and lay your eyes on the valves. You'll be able to see most of the valve for that cylinder through the intake port:

Or, buy an endoscope camera and put it through the spark plug hole. Just make sure that it has a dual camera head on it.

I caught this pic pulling the scope out of one of the cylinders that I took pics of for my thread in the XC90 forum:

It's an inexpensive camera from Calvan Tools that hooks up to your phone.

 

Burnt valve in cylinder 3 usually means the head is warped. This engine does not have hydraulic lifters, unfortunately. You have to take the valve cover off like every 100-150k miles and adjust valve clearance.

 

That is the first I have heard of that. Are we talking about the B5244S and B5254T2?
Reason I ask is because it is not just a valve cover. It is a cam cover and cam bridge and removing it involves removing the cam belt and cam sprockets. Not a trivial task. It also requires special tools to remove this cover without damage.

 

I came across an identical misfire on cylinder 2 of a C70. After lots of tests and investigation it turned out to be a vacuum hose that had popped off and was only causing a misfire in cylinder 2.

 

Since I ran a compression test and got 0 psi in my problem cylinder its unlikely that that is my cause but definitely good advice for others who stumble across this thread to check out. Thanks for the suggestion

 

I feel your pain. My mom's 2016 XC60 T5 somehow ended up with a burnt up valve. Had it confirmed by my mecanic and the local dealer. Considering how she does not push her cars nearly to the level I do, it was unexpected and disappointing.

 

If you have a B4204 it might be the turbo (bad design) leaking oil. Pull the intake and look to see if oil is inside it. If so, just replace the turbo, intercooler, and clean the intake and ducking. Your problem should be solved.

 

How would this cause a misfire and no compression though? Could be one of the reasons I had higher amounts of build up on the engine, but im not sure how fixing this will solve my no compression problem without addressing valve build up and potentially damage?

 

Check the PCV banjo bolt pin...

 

I did the PCV when I got the car a year and a half ago so it should be fine but ill have a look when I tear everything down to be sure

 

You'rd need to understand what caused the misfire in the first place.
It could be oil rings, or bad injector, and address that.
At this stage, opening up the engine would worth a full refresh, like piston rings and bearings, upon case.
Take your time, it's a nice project as it sounds, despite the happenings.

 

You'rd need to understand what caused the misfire in the first place.
It could be oil rings, or bad injector, and address that.
At this stage, opening up the engine would worth a full refresh, like piston rings and bearings, upon case.
Take your time, it's a nice project as it sounds, despite the happenings.

Yeah, ive already done the testing to rule out injector, coil, and plug and know its a compression problem. No signs of head gasket issue so my prediction is a burnt vale from giving it the beans under full boost, not an uncommon problem when there is buildup in an older engine. Im going to assess the valves further and likely do a refresh of just the head for now (valve seals, lapp and or replace valves, head gasket, cam seals, ect.) Not sure if I have it in me to refresh the bottom half of the engine as well (pistons, bearings) but im still deciding and might change my mind based on leak down test results. While I have the head out I will replace random stuff that is exposed as well such as the turbo oil return line seals and more.

 

This thread is devolving quickly. Not sure what a borescope or additive will tell you - the head needs to come off at a minimum, so start there. This sounds like classic burned valve.

 

Agreed.
Borescope would confirm what he'll find out when pulling the head. I mean, if you have one you can take a look, I don't think OP has one or he would have said so.
Not necessarily a common issue of these burning valves but when you have one cylinder on this engine with zero compression and no other symptoms, its almost always a burned valve.
In one case, I've seen the PCV banjo bolt check ball escape and got sucked into cyl #1 and cracked a piston, though its always #1 as the banjo bolt is in the #1 intake runner.
Bottom line the head has to come off. They are not difficult to remove.
Though the one about flushing the engine made me chuckle.

 

My 1998 S70 GLT 2.5T burned #3 exhaust valve at 180K miles. I unplugged the electrical connector to #3 injector and drove it for a while.

 

Pulled the head and valve 3 is burnt. All the other components are in great shape. I have a donor head that has but the exhaust valves have a good amount of buildup. Wondering if it will clean up when i lap the valves or if i should replace my one burnt valve with a new one. Mine are the ones in the vans cardboard and the single one is from the donor head.

 

Nice work. Cleaning up and using the used valve you have pictured should be fine.

 

Mine look similar to yours. The engine started consuming a lot of oil a few months before the end, I found a lot of limestone-like deposits inside the combustion chambers. That warranted a set of new piston rings and honing the bores.

 

The faces and seats will be cleaned during lapping.

 

How I did the valves cleaning. SimpleGreen in one beer can, muriatic acid in another. Put both on fire. Dip the valve into acid for a bit, then into SG. Wipe with a rag, repeat. Acid will consume the liner of the can and then the can itself, so have an empty beer cans supply steady.

As said before, don't dip the valve's stem deeper than where it travels in the guide, or you'll ruin it. Also don't scrub the stem.

Coat with WD-40 or PB Blaster afterwards.

 

That looks way better than what I’ve been trying thanks!!

 

Want to replace the thermostat gasket before it goes back in, does any one know of anywhere i can get the gasket thats in the middle? my understanding is its not available and you have to replace the whole thing, kinda dumb. should i just use rtv?

 

I would not trust RTV as a gasket on that. If you can't locate the seal, it would be best to get a new thermostat. You don't want a coolant leak after just doing the head.

 

if you can wait, Rockauto has them under Thermostat / Thermostat Housing / Water Outlet Seal

 

Those are all for the surface between the head and the thermostat and included in the gasket kit im getting. There is another gasket in between the 2 thermostat halves that i cant find

 

You have gone this far, I'd recommend replacing the valves, using Volvo or Mahle brand.
If tight on money, the replace all EXHAUST valves x 10 bc the exhaust valves are usually the ones that burn.
Intake valves rarely ever burn (they are cooled by incoming fuel).

Of course new Valve stem seals, Volvo or ? Corteco.
Ton of info in MVS forum...

 

New Volvo exhaust valves are $650 + taxes.

There's nothing wrong with old valves. They burn not because the metallurgy degrades, but because valve is not sealing properly anymore. That could be due to lack of valve/tappet clearance or something got trapped between the valve face and seat.

Exhaust side valve stem seals are Volvo only, others don't last. Intake can be Elring.

 

The exhaust valves burn bc of age, heat and oil leak...

Just give enough time, mileage, any exhaust valve will eventually burn.

The main issue is improper seating, when the valve does not have full contact with the surface when in a closed position, it cannot dissipate heat properly, thus burned valve.