I have a 85 gsl (automatic). It seems like it takes longer and longer to get the idle smooth after start up. After driving for a half hour using the choke out it would idle at 950 rpm. In the last few days the car idles at 650 and less (warmed up or not) and surges sometimes, at first it would struggle under load from the transmission, but now even in P or N. It seems warmer outside when I get out, clogged cat maybe? No loss in power or rough idle while driving or accelerating though. I checked vacuum lines and changed the cap and rotor so far with no improvement. Any ideas on what to try next?

 

I would...change the air filter, tighten up the carb bolts (not too tight!) and just retune the carb. If the problem comes back, I would have to suspect the cats.

 

When I owned it, it always idled low...that is odd...