Checklist for Reliability of Older Audis

[Huw Powell]

On 8/16/2011 12:04 AM, Marc Boucher wrote:
> Huw I respect your tremendous knowledge, and all the assistance that you
> give to everyone on this list. But isn't there a list of generally known
> weak-points to the I5 / NF engine that are worth changing out?

Sure, anything made of rubber or plastic.  Other than that?  No.  That's 
why they are so awesome, they run forever, like Volvos.

> Your argument, "A 20 year old transistor died. It happens.", seems to
> offer full support to those that say, get a new car so you have
> something reliable.

Transistors can die at 2 years just as easily as at 20 (but less often). 
  "New" stuff always has the problem of unfound bugs and mechanics who 
haven't learned the system yet.  The bug in the 88-92 A90 is the ("new") 
dashboard switches - everything else was made really good over the 
years.  If your issue is indeed the ignition booster, it's the first one 
I've heard of going bad, so it's a not a common item.

> For example, I'd often wondered if I should have replaced the ignition
> coil at the same time as I did the distributor cap, rotor, plugs, and
> wires. And if I'd replaced the coil, perhaps the transistor on the side
> of the coil might have been sold along with the coil.

I have 4 or 5 spare coils so I don't worry.  Also, I have never heard of 
one going bad.

> If I recall correctly, you design a line of speakers. One of my old set
> of Kef speakers is notorious for the capacitors drying out over time,
> and requiring replacement. People often simply purchase the aftermarket
> crossover units which are designed with newer technology and
> 'supposedly' yield better frequency separation between the midrange and
> tweeter. So, while it would be impractical to replace every electronic
> component in a 20 yr old car, I was just thinking that there might be a
> hit-list of those that fail most frequently.

Electrolytic caps go bad with age - especially if not used.  Film caps 
are much more reliable, and sound a miniscule bit better.  There are no 
"frequent failures" that are electronic on these cars.  Sure there is 
stuff that goes south with age, but there's no easy "replacement 
schedule" to follow that would make sense.

Do all the vacuum hoses sometime.  Undo all the electrical connectors, 
clean, add dielectric grease, and reassemble sometime.  Do the entire 
cooling system (hoses, stat, heater core, water pump) on your next 
timing belt change.  Pull all your fuses, clean, replace.

Spend $500 and rebuild the entire fuel pump/filter tray (wait, you have 
a 100, right?  Pump in tank, filter in engine bay, never mind, on my 
cars they are in the LR wheel).