2.4t cylinder one misfire mystery......

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Evening all. Just bee lurking to try and find information but I thought I better post something instead.

I have a 2001 v79 2.4t (200) and it has a misfire. I know what your going to say but this happens only when it’s hot!!

Now the car has 175,000 and runs on lpg which is custom fitted before I bought guy it. Loads of history etc.

Anyways the car runs fine when cold but when it gets hot it misfired. I get a pending code and then a proper code which is a p0301 (cylinder one misfire detected). The car has almost new Volvo plugs which are gapped for lpg which is about 0.1mm less than normal. Pulled them out to inspect them all and cylinder one is blackened and wet from not firing. The rest are your normal colours. So I moved cylinder one and two around and started the car. It missed and before I did that I cleared any codes. Cylinder one misfire. Then I moved the coils. Same thing the fault didn’t move. I cleaned the earthing points on the head casting and cleaned the connectors and made no difference.

Fitted brand new coils and although the car starts a little better but still misses when hot. I then did a compression test on all cylinder with engine hot and I’m getting 200 psi across the cylinders. So as far as I’m aware the compression is good and yes all plugs were removed and throttle was wide on en. The car also misses in lpg as well as petrol so I have ruled out blocked filters or anything like that. Air filter is new also. Then disconnected the battery and shorted the power cables out and left it for half hour and then went under the bonnet and cleaned all earthing point I could find. I also gapped the plugs to 0.7mm to see if it would make a difference. Took the crank sensor off and cleaned that. That was very black and full of crud but yet didn’t make a difference after I put everything back together. Spark plug was tested against the head casting for sparking and I get small sparks when grounded to the head and they spark between the electrode and the tang and as you pull it further away the sparks are very bright and powerful so I think I have a good earth? Unplugged each coil when cold and the engine suffers and then regains strength. Done on all cylinders. When hot however I unplug number one and nothing happens but the rest react.

I’m running out of options here. I didn’t have a head gasket issue as that’s been recently done so no coolant in oil or the other way round. All filters and fluids have been replaced on including lpg.

What else can I do. I can’t think many more things that can cause a misfire. Is it worth putting a new crank sensor in. I have been told that everything is timed off of the number one cylinder.

Like I said it happens when engine is fully put temperature after about twenty mins of slow and fast idling and revving on both petrol and lpg.

Ryan