P0302, misfire cyl. 2

[gXX]

I have a Aygo 1.0 from 2007. I got fault code P0302, missfire cylinder2. I removed the spark plugs, the one on the cylinder 2 showed signs of typical "pre ignition". Anyhow, I changed all spark plugs - but the code is still there. I moved the coils around to see if the problem followed the coil - It did not.

I've removed the coil and the plug to see the actual spark on the plug. And yes, there was a nice spark.

I then checked the fuel rail, and oh yes. There was fuel! I removed the injectors and ultra sound cleaned them. I made sure to move them around as well to see if the problem moved to another cylinder. It did not. Still missfire cyl2.

I then checked for vacuum leaks with "starter gas", and no signs of any leaks.

Now, I've removed the valve cover to oculary check the valves and timing chain. Everything seems fine there as well.

My next test will be a compression test - I've just ordered tools for this. Is this the right way to go? And/or can I check something else while I wait for the compresson tester to arrive?

Thank you!

[gXX]

OH yes!

Compression 9 + 0 + 9. Funny stuff, not. What is most likely here?:

• Burnt valves
• Cracked head
• Bad head gasket
• Killed piston
• Piston rings? (don't think so since the compression tester didn't respond to added oil in cylinder)

I also noticed that the coolant was "brownisch" to a level that is very unusual. The engine oil seems fine. And i've not noticed either unusual oil or water consumption.

Wondering if I should replace the engine or diagnose further. The engine only has 62k on it.

[furtula]

Check for bubbles in coolant while engine is running, usual symptom of bad head gasket. 

 

[gXX]

I did, and there is nothing. Will try to do a DIY leak-down tomorrow.

[gXX]

OK, I did a home made leak down, placed the cyl 2 in TDC and started the compressor. Every little piece of air goes right through and out the exhaust system.

So conclusion - dead exhaust valve. Time to replace the engine 🙂