Volvo S40 cylinder 4 misfire

choons

Hey folks, I've been trying to fix an engine misfire but no progress. Any thoughts appreciated before I give up and go to a garage!

10mins in to a drive and noticed low power, when I slowed down could feel engine running rough. Has not ran smoothly since then (not intermittent).

2005 Volvo S40 1.8L Petrol
145,000 miles
Error code P0304 - misfire cylinder 4

Have replaced spark plugs and ignition coil - what's next?

Polo_Cluvie

Possibly injector

scannerd

compression test

choons

Polo_Cluvie wrote: »

Possibly injector

I tried running the engine for a few mins and then taking out the spark plug. There was petrol on the plug so I think we can rule out injector now. Thanks

scannerd wrote: »

compression test

Ended up getting a garage to run a compression test - no compression on cylinder 4. Thanks.

Going to start Googling but it's not looking good!

jca

No compression at all?

choons

jca wrote: »

No compression at all?

No, garage said nothing at all.

Cylinder 1 was down on pressure but nothing serious and then 2&3 were okay.

mullingar

choons wrote: »

Ended up getting a garage to run a compression test - no compression on cylinder 4.

Get the garage to do a leak-off test.

Basically this test uses compressed air into the cylinder and you can roughly measure the gas-tightness in %, if its low, you can find the source of the leak by listening to where the gas is escaping from. Escaping compressed air can only go one of 4 ways via leaking rings, leaking exhaust valve, leaking inlet value or leaking head-gasket

choons

Just a follow up:

Leak test in a garage confirmed no compression on cylinder 4. The garage quoted 1000 minimum to open up with no guarantee they could fix it.

Decided it wasn't worth doing in the garage but a friend was able to take a look over the last few weeks. Removed timing chain, AC kit and a few other parts. Took off the head and found that one of the valves had a chunk missing. New valve & head gasket installed and have it running on 4 cylinders again.

Idling a bit high but seems grand apart from that! Will investigate this when I get a chance.

mullingar

Idling high could just be a vacuum leak

jca

Do you know what caused the valve damage? Was the valve burnt away? I always like to find what caused the damage otherwise it will just happen again.

jca

mullingar wrote: »

Idling high could just be a vacuum leak

Causing a lean mixture which valves don't like.

choons

jca wrote: »

Do you know what caused the valve damage? Was the valve burnt away? I always like to find what caused the damage otherwise it will just happen again.

Not burnt away - almost like a pizza slice chunk missing from the flat valve disc. I'll try get a picture!

No idea what caused it but would be good to find out.

JustJoe7240

choons wrote: »

Not burnt away - almost like a pizza slice chunk missing from the flat valve disc. I'll try get a picture!

No idea what caused it but would be good to find out.

only thing that would concern me is where the chunk is now!

jca

Was it an exhaust or inlet valve? Have you still got the high idle?

jca

joecass123 wrote: »

only thing that would concern me is where the chunk is now!

Partially melted in the cat.

choons

JustJoe7240

choons wrote: »

Looks like it's been burned out rather than a lump breaking out of it?

jca

That's a big chunk!! If its an exhaust valve it's very black, they usually are a light brown colour.

spiggotpaddy

joecass123 wrote: »

Looks like it's been burned out rather than a lump breaking out of it?

Bit of araldite. Be grand.