knock sensor and "consumer vehicle" search ended in a QUATTRO

[Andrei Kogan <abk@phy.duke.edu>]

Hello,

First,

Our "consumer vehicle" search ended quite unexpectedly --- three days ago,
we bought a 1988 audi 90 quattro. We decided that we don't need a bigger
car all *that* much and agreed that the size is at the end of our list of
priorities, behind reliablility and the car being an Audi.  It has 160,000
miles on the clock and the question now is how do we help it go for another
100 -200,000 . Hence my question:

1. One thing that the car *needs* is the engine tune-up. I can hear a
noticeable ringing under hard acceleration as if the ignition timing is
off. Our mechanic told me though that this car has a knock sensor and
should be able to take care of it on its own. The car came with a half-full
tank of gas, I topped it with a 93 octane and this seems to have improved
things, but hasn't  eliminate the problem  fully. I am taking it to the
mechanic on wednesday but would appreciate any suggestions for
troubleshooting before that. Also, can anyone explain how the knock sensor
works?

2. This is no big deal, but I wonder if there exists a low cost solution.
The trip computer doesn't want to reset. And Occasionally it is showing
some nonsense like 60 miles per gallon when the car sits at a stop light.
suggestions, anyone?

3. I understand the consensus is that mobil 1 oil should be used in turbo
cars.  Ours has a regular non-turbo 10V engine, but I am wondering if
synthetic oil would still be a better choice. I am planning on keeping the
car at least for 5 years and would like to know if you think it would be
worthwhile to switch to mobil 1. Also , what grade? I am using a regular
20w50 in our 4000S which burns a little bit of oil and, for that reason, I
thought using synthetic in it was not cost-effective. Any opions?

4. I am going to check the timing belt. If it needs to be replaced, would
you recommend to do the water pump/ idler pulley at the same time? (Does
this car have an idler?) 

5. Overall, the car is in good shape mechanically and cosmetically. The
suspension, however, is softer than our 4000S's which has 3 year old BOGE
shocks. It seems that the struts on the quattro are still original and may
need to be replaced in a year or so. Otherwise, could you please give me
your suggestions as to what to check on the car (e.g. should I replace the
oil in the differenial / gearbox etc). breaks/driveshafts are good.

Thanks, Andrei


1984 4000S , still in for autobox valve transplant
1988 90q, all working door handles