M13a engine light and misfire.

have a look at helicoils, that might be the solution you need there

You can get spark plug thread chasers which might do the trick. They are double ended for the two thread sizes normally used. Ebay or if you are near Halfords or Machine Mart (£5.99 CHT261 That price was last years so it might be more now) Worth a try. If he had not torque loaded them then they probably worked loose, except of course the cross threaded one! Ali heads need to be treated with care and torque loading all fittings is essential.

[/Will try the thread chaser first the if that doesn't work l'll give the helicoil a go. Thanks. sup]

For aluminium threading, use Denatured alcohol on the tap so the threads gets smoother. Cuts better with etanol for some reason.
Not sure how to, but it could help to put air pressure inside the cylinder to blow out debris from cutting..

If it was steel cutting you could put grease on the tap and hope the debris got stuck on it..

And helicoils are not my favourite. They often leak as well you will need some thread locking and sealing compound on them.

looking at the heli coil type repair it looks like you have to snap off a tab using long nose pliers which won't work with the head on the engine. There is a a german v coil system which doesn't have a tab. any one used one of these?
I'm also wondering how difficult it would be to remove and replace the head myself. it's mainly the engine timing i'm worried about.

Have you worked on engines before or/and do you know the basics of how an engine works? The crankshaft rotates twice to the camshafts once is the important thing to know. Timing is straight forward as long as you align the camshafts and crankshaft correctly so with the crankshaft at top dead centre i.e piston no I ( one at front of the engine) at the top of its bore and the valves of that cylinder closed will be the datum point for removal and refit. But try the thread chaser first. They do work with care. Getting it started in the right place is the key. The head being aluminium and the chaser steel can lead to a false thread being cut.

Well she lives. The thread chaser i bought was the double ended type. But you cant get a socket onto it because the big end doesn't leave enough clearance. So i went with the V coil system. Got the engine at TDC so the valves were closed. Using the re-threading tool supplied i packed it with grease and after every 2 turns i pulled it out and removed the swarf and old grease then re-packed it.
Looking down the plughole i could see some grease and some swarf on the top of the piston. used a welding rod to pick up the worst of this. I then used a long blowgun and nitrogen gas at 6 bar (No compresser) along with a can of contact cleaner. Sprayed a load into the head then used the blowgun to blow everything out.
De-greased the v coil then applied high temp loctite. Tightened the plug down and left it overnight. Fitted new coil pack started it up.
No smoke or weird noises. Revved it a few times then took it out for a drive for 10 miles around local roads.
temperature ok. No smoke or weird noises. The only issue is the engine management light stays on. But the car runs fine.
I know i've been very lucky to not do any further damage.
Thanks for the advice supplied regarding my options.

Great!!

Engine light will have to be reset with a tool you hook up to it, or you vcan try unhooking the battery for a while. Could help with five minutes, but a proper reset of half an hour will do it better i think.

Thanks that worked. Disconnected battery while i gave her an oil and filter change. That cleared the fault light.

If anyone is still interested, Wurth make a product called Time Sert.
Never tried them myself but if Edd China is to be believed, they're superior to heli coils.
Here's a link to him demo-ing them:
Readily available on ebay.