Kenneth Madsen wrote:

> I recently took the 87GL 2wd for our mandatory emmisions testing here in
> Ontario, and failed.
> Which parts of the engine should I be paying attention to when tuning it to
> tolerable levels.
>
> I was thinking replacing spark plugs, wires, distributor cap and rotor, fuel
> filter, air filter, changing oil and timing.
>
> Can anyone else give some insight or tips for a good tune-up?
>
> Ken Madsen
> Toronto Ontario
>
> 87GL (Flash)
> 87 Golf Diesel (Smokey)
> 95 Jetta GLX (Black Beauty)

Any significant vacuum leak will beat you.  Check very carefully.
New air filter, or take it out temporarily.
If the oil hasn't been changed recently and might have some gas in it, the vapor
being drawn into the intake may be making it run rich.
New plugs if they are due.
It is important that the ECU is getting a proper signal from the O2 sensor and
goes into closed loop operation.  Check this if possible or else as a last
resort just put in a new sensor anyway.
Exhaust leaks can cause air to be drawn *into* the pipe and fool the O2 sensor
so that the ECU makes the engine run too rich.
  A slightly higher idle speed and a slightly later spark than normal might help
during the test.