Why would a 4000 5 cyl vibrate/sound rough?

["Luke D. Vinogradov" <Luke.VINOGRADOV@ENG.monash.edu.au>]

Hi,

I'm looking for a 4000/80 5+5 auto around '81/2 and have examined 
several.  There are not many available in this country, and most of 
the bodies are pretty bad, as I gues you'd start to expect for a car 
of this age.

Anyway, I've found one which has a good body, straight, no rust and
also a great interior.  However, when I drove it, it seemed to
vibrate uncomfortably at idle, and this didn't smooth out at higher
revs, just kinda got faster.  It's hard to describe it, a little
like missing a cylinder, I guess, but not as severe as that.  It was
definitely worse accelerating under load than just revving in N. 
The car has done about 230,000 kms (~143k miles) but doesn't seem to
blow any smoke, and didn't really seem to be lacking in power.  The 
trans is of unknown origins, having been tacked on by the dealer 'cos 
the old one had had it (and he can't even pronounce Audi!).

Could there be a (relatively) cheap/simple cause of this, such 
a clogged injector or collapsed mounts, or does it sound like 
something worse?  The car is cheap enough that I could buy it and get 
a changeover auto or new mounts or overhaul the injection system or 
whatever, but I don't want to have to go too far (i.e. new engine!).

Can anyone help with this, and/or offer any general comments about 
this model...

Thanks,

Luke


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Luke Vinogradov    Driving Simulation Group
Monash University Accident Research Centre
Wellington Rd, Clayton VIC 3168  AUSTRALIA
Email: lukev@its-menz.cc.monash.edu.au
Phone: +61 3 9905 5545  Fax: +61 3 9905 5446
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