89 pontiac 2.8L surging idle

I have a 1989 pontiac 6000 with the fuel injected 2.8 liter v6 that has
developed a problem with surging/low idle.

The car starts and runs fine when cold (first started in the morning) but as
the engine warms up the engine begins to idle strangely and it surges from
high to low high to low until finally the idle is so low that it stalls. I
can't even stop at a stop light without the engine dying on me.

The engine had a recent tune up so I highly doubt that spark plugs are the
problem as it runs fine on high idle.

What could cause this?


I was thinking that it could be the following:

1. Bad ignition module
2. Bad fuel injectors
3. Clogged throttle body.


Can anyone recommend a course of action for me? The car has 300,000km's on
it and I'm the original owner and I have cared for my car since the day I've
owned it.

Thanks a million