BlueWagon

So it does it at 90, or before it gets to 90? Because thos makes it sound like it doesn't happen if it is warmed up to 90? So how long before 90 does it run rough? Eg, when you first start or say 5 minutes after? Can you explain the sparodic problem? Why exactly did you change it? So are you saying every time between 80 and 90 it runs rough but you can still do 140 kmh no problem? I would avoid just changing parts without good reasoning because it will cost you alot and unlikely to fix much. Really need to do some diagnostic work. For example, next time it runs rough, try stopping and seeing if it idles or you can rev it freely in neutral? Try turning the engine off and restart and see if that helps? Does it blow black (or white) smoke when running rough?

Maybe an aluminium crush washer or O ring? You can put the oil you drain from the box back in if its very fresh. Just make sure you drain into a clean container

I have not removed one but if you are saying the pulley turns and this the engine turns when you try to undo the bolt, maybe try locking the engine up. If manual try in gear with handbrake on. If auto or dsg need to use a breaker bar on the crank pulley

Grab a few sizes and see what fits. If 40 doesn't, try 45. If too loose, try 43. T45 rings a bell for me but you are the one looking at your car. You are best placed to choose the correct size

Do you mean the stick won't move into the right position for 5th and Rev? Maybe a wasp or rat nest blocking the shifter on the box. Have a look while someone moves the stick inside. Maybe a bit of wd40 on selection cables too

Can you select these gears with engine off? Maybe clutch just a bit gummy so won't let you push into the gear. Maybe ride the clutch a bit to clean up the plates

I would and certainly do on any car I have the clutch out of. Also replace spigot bearing and thrust bearing

Clogged air filter or dirty sensors on intake side??

Could you just monitor oil temp on the dash display and back off a bit when it goes over say 140C.

Maybe...but what are you going to do about it? Probably wait until it either dies or starts really making a song. Id just be aware of it and monitor it. My Landcruiser one makes a fiar noise and I know its gonna die some day....but probably just let it run on until it stops working

Sounds like the noise of the AC compressor working. If it cools fine and the noise isn't that loud under the bonnet, Id probably just go on living my life and let the compressor work away as it should. My suggestion would be to have someone cycle the AC while you listen under the bonnet if you are really worried, but other than tinkering with the AC compressor its probably a leave it alone kind of thing

Why? Can they not use degreaser and a hose? Id do the same if I were you. Just wash engine bay with spray degreaser and water at car wash close to garage. No need for steam clean

Does it make the sound with engine turned off. Might be easier to answer if we can hear it with the engine turned off

Personally Id just go to the dealer and get a genuine one. In Aus they are about $35....which isn't too bad for something made in Europe and you know isn't cheap Chinese junk. Or, local auto parts store and get the recommended Ryco or Mann filter. They will have a book with all the applications

Did you check coolant etc after overheating? Maybe water in the combustion chambers. I can't see how a water pump could cause a misfire and stall. No way. If it jambed it would just snap the belt. Im thinking an electrical issue there. Bad earth....