Failed compression test and misfire

[amorlv70]

Hello.
Over the last 3 months my car developed a slight misfire at cold on cylinder 5, which quickly cleared up after 30 seconds or so.
It is on 146,000 miles, LPG fitted at 115k.
I replaced the spark plugs, then the coil of cyl 5 and it made no difference, so I stopped using the car as the misfire was getting very bad.
Fastforward a few weeks and I have done a compression test, it has failed quite dramatically:

Cyl 1: 165psi
Cyl 2: 65psi
Cyl 3: 90psi
Cyl 4: 65psi
Cyl 5: 30psi

To me this is obviously not right, and I can probably rule out plugs and coils.
I have no symtoms of HG failure coolant is still green and oil normal colour. So is it possible that my head has suffered with valve recession?

I was under the impression that these cars don't need flashlube as they have hardened valve seats. My fitter didn't install flashlube so I assumed it wasn't necessary.

Before I take my engine apart, does this sound like a valve problem? Should I try and source a new engine/head?

This car is very sentimental, and has been looked after meticulously, so I will give it whatever it needs.
Thanks

Edit: Is there anything else that could be the problem? Piston rings? Spark plugs on the problem cylinders are pretty fouled

[Simmy]

it sounds like a valve problem. i would remove and inspect. it would be worth getting all the valves guides seals and seats done while the head is off . if vou are running solely on lpg i think you need to up grade to the lube system your readings show only one good cylinder compression.

[classicswede]

Looks like valve issues on 4 cylinders,

You could try checking and adjusting the valve clearance but cyl 5 looks so bad I suspect you are going to have to take the head off and replace some valves and have the seats recut

What are the car/engine details? Some need a valve oiling system

[amorlv70]

Originally Posted by Simmy

it sounds like a valve problem. i would remove and inspect. it would be worth getting all the valves guides seals and seats done while the head is off . if vou are running solely on lpg i think you need to up grade to the lube system your readings show only one good cylinder compression.

I recently realised that I forgot to do wide open throttle when testing, would that make any difference? I will get the head off when I have time and have a look. Do I need an entire new head or would it be salvagable do you think..
It was running with those numbers (albeit rough at cold!)
Thanks

[amorlv70]

Originally Posted by classicswede

Looks like valve issues on 4 cylinders,

You could try checking and adjusting the valve clearance but cyl 5 looks so bad I suspect you are going to have to take the head off and replace some valves and have the seats recut

What are the car/engine details? Some need a valve oiling system

Yes it does, as I said above is full throttle application key when testing compression? Fuel pump fuse was pulled.
Cyl 5 was the one reporting a misfire so it makes sense..
So can I get the existing head sorted or will it be new head time? Sorry I am still learning, done most other jobs on these cars but never taken a 5 cylinder engine apart.

The car is a 2004 pre-facelift (2004 my) v70 with the 2.4 170 B5244S 2435cc.

Thanks very much for your reply, much appreciated.

[Simmy]

a full head refurbishment is needed. remove it and take it to an engine specialist who will advise on what is required they will have all the right equipment to replace the failed components . do it all not just the cylinders with problems . do it right do it once. line up all the relevant timing marks before disassembly

[classicswede]

Originally Posted by amorlv70

Yes it does, as I said above is full throttle application key when testing compression? Fuel pump fuse was pulled.
Cyl 5 was the one reporting a misfire so it makes sense..
So can I get the existing head sorted or will it be new head time? Sorry I am still learning, done most other jobs on these cars but never taken a 5 cylinder engine apart.

The car is a 2004 pre-facelift (2004 my) v70 with the 2.4 170 B5244S 2435cc.

Thanks very much for your reply, much appreciated.

There is no likely reason why it should not be possible to repair the head you have.

[amorlv70]

Originally Posted by classicswede

There is no likely reason why it should not be possible to repair the head you have.

OK. I will get it pulled off when I have time in the early days of March.
I have a couple of questions:
-If I have burnt or worn valve seats, could this have been caused by an improper tune or the car running too lean on LPG? It is a BRC system.

-I am using genuine volvo spark plugs, and was told that would be fine (they have 3 prongs), from what I gather that is not right.. Is that the case? Should I change the plugs once completing the job?
Thanks ClassicSwede.

[amorlv70]

Originally Posted by Simmy

a full head refurbishment is needed. remove it and take it to an engine specialist who will advise on what is required they will have all the right equipment to replace the failed components . do it all not just the cylinders with problems . do it right do it once. line up all the relevant timing marks before disassembly

OK, Cheers. Best sell my S60 then to free up some £ to fund it

[classicswede]

Originally Posted by amorlv70

OK. I will get it pulled off when I have time in the early days of March.
I have a couple of questions:
-If I have burnt or worn valve seats, could this have been caused by an improper tune or the car running too lean on LPG? It is a BRC system.

-I am using genuine volvo spark plugs, and was told that would be fine (they have 3 prongs), from what I gather that is not right.. Is that the case? Should I change the plugs once completing the job?
Thanks ClassicSwede.

You have still not said what the engine is
If the engine is a type that needs a oiling system then that can be the problem
A failed injector, poor tune, failed sensor and a number of other things could have caused it

Spark plugs the Volvo 3 prong plugs are not the best choice, I convert to NGK single prong plugs