Failed compression test and misfire

amorlv70 · Feb 15th, 2023, 22:24

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

Feb 15th, 2023, 22:24	#1
amorlv70 Junior Member Last Online: May 13th, 2024 12:15 Join Date: May 2020 Location: Newcastle View Photos By: amorlv70	Failed compression test and misfire 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 Last edited by amorlv70; Feb 15th, 2023 at 22:45.

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