Jetta mk2 petrol, reasons for loss of power other than fueling & ignition

Question

I'm planning on buying a 1989 VW Jetta A2 with a 1.6 carb engine and automatic transmission. The particular car I'm interested in is generally in very good condition, except for being low on power and stuttering while accelerating. The owner says that the carb simply needs adjustment, which would be fine as I have some experience with Pierburg 2E carbs. However what seems a bit strange for me is that the symptoms are identical when running on petrol and LPG (as the car has LPG). Based on my previous experiences with such engines I would assume carb tuning shouldn't affect running on LPG, as the only element used when running on LPG is the throttle valve.

Idle is quite smooth, so it appears to run on all cylinders.

It could of course be a matter of a vaccum leak between the carb and intake manifold, ignition problem or some other minor issue which wouldn't prevent me from buying the car.

However my question is whether it could potentially indicate some major issue with the engine itself or the automatic transmission?

Thanks.

Answer 1

Having much experience with this engine, I'd say that the likely cause of the problem is the rubber foot / gasket upon which the carburetor is sitting. These split and begin to pull in air which can cause lean running. This would be the very first thing I would check.

Answer 2

I eventually bought the car. After a bit of searching it turned out the issue was caused by wrong choke plate setting - the bimetallic spring tension was to low and sometimes the choke was kept open too much when cold and sometimes it didn't fully open after warming up. Simply turning the autochoke mechanism by a couple of degrees solved the problem.