Hopefully this will be of help...
In my opinion with C4’s buy as late a car as your budget or personal preference allows. While there is nothing inherently wrong with any car from 84 and up, with each year more features were introduced, existing parts and features were developed further, power went up, etc, etc.
- Dash display – make sure all of the LCD panels on the dash work, illuminate properly and are not broken. LCD panels can’t be bought individually and you are looking at AUD $650 and up for a repaired or remanufactured unit.
- Get an insurance quote before buying – they aren’t cheap to insure.
- If looking at a 4+3 manual make sure the overdrive unit works and everything operates reasonably smoothly. 4+3 overdrive parts are not always readily available. Parts for the gearbox itself shouldn't be a problem though.
- Make sure the service engine soon light illuminates when the accessories are on but that it goes out after the car is started.
- Make sure the steering is smooth and that you can move the wheel from lock to lock without the tyres fouling – you’d be surprised with some conversions…
- Do a tight low speed u-turn to listen for any knocking in the diff.
- Check the wheel bearings, they can last for over 100,000 miles but when they need changing they will cost at least AUD $500 each for the fronts and probably AUD $300+ each for the rears.
- Make sure the AC, cruise control and other features work properly – especially the AC.
- If you are looking at one with interstate rego, make sure you get a blue slip (AUVIS) inspection beforehand to make sure you won’t have any problems transferring the rego to another state.
- That’s all I can think of right now. Off the top of my head the most commonly referred to 86-89 maintenance items include alternators, LCD dash’s, and 4+3 overdrive units. That is not to say you will have problems with the above if you buy a car so equipped. As an example my car needed new alternator parts over three years ago and has been fine since (touch wood) and none of the receipts I have from the previous owners show any alternator problems...