Tappets hell

Can anyone steer me out of my tappets hell?

I replaced the head gasket on my 2003 Jimny.  It's the deepest I've gone into car mechanics before beyond standard maintenance jobs, thanks to a lot of help from Google Gemini and this forum.

Everything went smoothly enough but now it sounds like a tractor.

After the rebuild, it started on first turn and ran beautifully - really smooth and quiet.  After running for about 20-30 minutes, it suddenly went very tappety - noisy and uncomfortable.

So I've now adjusted the clearances three times:

• First time, a mate told me to set them all to 6 thou (I can't remember where he got that info from), but that made it worse.

Google gives a range of 5-7 thou on the intake and 9-11 thou on the exhaust valves, so

• Second time, I left the intake valves at 6 thou and set the exhaust clearances to 10 thou.  That made it very much worse. Very noisy with sluggish and lumpy revs.
• Third time, I set the intake to 5 thou and the exhaust to 9 thou. That made it slightly less worse than the second time, but still really bad.

I feel like I'm going round in circles.  Any tips?

Maybe we should start by identifying what engine you're dealing with - most folks would assume a 2003 Jimny with an M13a engine, but that is a shim over bucket arrangement, which does not lend itself to the sort of adjustments you're describing.

Could it be that you have accidentally disconnected a connector to a sensor or damaged its wires? A diagnostic computer would swiftly tell you if that is the case.

Ah yes, good call. It's the G13BB.

Hadn't thought of that. The crank case sensor is a bit untidy. Maybe an intermittent connection? I'll have a look in the morning.