Re: Results & 2 questions :)

[zm@mhcnet.att.com (Zafer Mehmood [209])]

> 
> How many miles do you have on your 5000? I've been toying with the
> idea of switching to synthetic in my 100Q for a while, but I've been
> told that it's a "bad idea" once you have more than a few thousand miles.
> Is this not true?

No, it isn't. You can switch to synthetic anytime. For new cars, some
recommend you wait until engine is broken in (a couple thousand miles).
Of course, this isn't your case. I switched to Mobil 1 on my 87 5000TQ at
around 90K miles (it has 128K now) and in my '84 Mitsubishi Starion Turbo
at 80K (it has 127K now) - no problems. The only side-effect of switching
to synthetic on a high mileage car is that if the engine is gummed up due
to infrequent oil changes, then the high detergent synthetics tend to
remove this gum and could potentially start minor oil leaks from previously
gummed-up seals. However, this is not a concern if the car has had a good
maintenance history.

> 
> > 2) my car over-vibrates about once a second at idle...and also, sometimes 
> > acceleration is a little hesitant...I assumed I had dirty fuel injectors
> > so I used quiet a few fuel-additives that were supposed to help...I didn't
> > really notice any improvement.  Could anyone please give me any hints
> > as to what it might be and what I could do about it?
>
 
I would check out the ignition system.  Do you have the Audi specified
Bosch tri-electrode spark plugs? If not get them. People have reported poor
idling with other plugs. Also check for corrosion on the distributor cap
contacts (inside) and the rotor. If the contacts aren't worn but have
black oxidized deposits, the deposits can be scraped off with a utility
knife. Also make sure the plug wires are snug and in good condition.

> Once again, my 100Q does this, too. My wife's 20V 90Q doesn't, I think
> because it idles higher (950 vs. 700 RPM). I think it may just be some
> kind of resonant frequency of the 5000/100 body at that RPM. I may try
> to adjust the idle, but that is not easy to do. How I long for that old
> carburetor screw you could just twiddle  ;-)
> 

700 RPM seems a bit low. The spec for my car (87 5000TQ) is 800 - 850 RPM.
There *is* a recessed adjustment screw on the top of the intake manifold
by the throttle, at least on the 86-88 5000 turbos (don't know about your
100Q). I would consult the Bentley manual before tweaking the screw - might
affect the emissions.


-----------------------------------------------------------------
Zafer Mehmood				   AT&T Bell Laboratories
zm@mhcnet.att.com			   Murray Hill, NJ