Certainly m8 but it really isn't that technical really, just common sense...... One sensor/relay/switch at a time!
First of all I was going to do an ECU reset proceedure anyway....(plenty of posts about it and how to do it) So..... I disconnected the battery first (make sure you have the radio code handy and your remote key fob works ok)
One thing that I didn't touch was the ECU itself
as I have been told that it can cause mayhem if you do disconnect it....
But mainly, I did all the connections to all the sensors that you can find in the engine bay from temperature sendor (on the thermostat) and everything that can be disconnected safely. I removed the top cover and cleaned the coil packs too!... The main things that need regular maintenance are the throttle body (butterfly) and the MAF sensor... Keeping these in clean, good condition can prevent a bucket load of issues.
You need a security type hollow torx bit to remove the MAF from its housing but make sure the little rubber seal is in place when refitting.
156.NET have a good tutorial on cleaning the MAF in the tips section.
I used isopropyl alchohol spray as it leaves no residue (maplins for around £10 but lasts years)
NEXT STEP... (not for selespeeds and V6's or any 156 with fly by wire throttle potentiometers mind)
The throttle body is best to use Carb cleaner and a spare person to operate the loud pedal while you clean it with a clean cloth after spraying... Once its as clean as you can get it, then use a very tiny amount of wd40 to make sure the butterfly is lubricated at the top and bottom.... The carb cleaner can often dry it out you see. Wipe it down again and refit all the clips making sure the induction pipes are fimly fitted and secure (I used new jubilee clips instead as I could still turn the maf housing with my hand once secured with the old clips!!!!! Not good really, is it?
The main important thing is to make sure that the airbox has a good seal as this is what usually causes all the problems further up the induction system. If a lug is broken then a couple of larger washers will resolve it but if the bolts are siezed, its worth while drilling them out and fit longer bolts from the main body and secure with nuts on the top instead.
I removed all the relays in front of the battery one at a time too and gave the connections a good clean, making sure that any rust was cleaned off and the contacts were all aligned before re-fitting.. I also did all the headlight bulb connections too for good measure.
Leave the yellow ABS plugs alone though
(either side of the top suspension turrets).... Removing these can cause possible error codes too
I also removed any earth cables that I could find and snded down the contact points and regreased with copperslip for good measure.
The next main issues are under the seats for the airbags etc... Safe to do when the battery is off. Just a simple disconnect on these some wd40 spray and re-connect every few months will keep the dash airbag warning light from coming on.
There you have it mate...
It took me a good couple of hours but once the battery was back on and ECU reset done, the car runs great.