Well, I think I know, but wanted to ask for some help first. I suspect I need some major work on the carb.

I have a 1985 GS 12A stick running really stock - no mods at all - 143K miles. About a year ago, I noticed the car really struggling to keep RPMs up at high revs. On the highway at 70-75, and going up a hill, I used to loose a couple of mph, but a slight pressure on the go pedal and it came right back up to speed. Now it seems to be bogging down and lumbering - it is pretty common to loose 8 to 9 mph and I have to kick in the 4bbl to bring it back up to speed. The 4bbl kicks in with about 1 inch left in the pedal - seems like it should kick in sooner.

The gas pedal feels stiff - I even felt the throttle stick momentarily. I unhooked the cable and it seemed to slide easily through the casing. I lubed it as best I could, but no change. It feels like it is searching for fuel andd just not getting it until I open up the 4bbl.

Replaced fuel filter - just because - no change. Cap, rotor, plugs - no change. The old plugs were NGK with about 45K on them and they all looked really good. Ran a can of seafoam thru it - no change. Fuel mileage is down slightly, but I suspect it is because I always have my foot in the 4bbl. Mileage is 19.5 combination city highway.

So, my suspicion is fuel delivery, but should I be looking at vacuum advance or anyplace else? Am I missing something obvious on the gas pedal linkage?

Oh, about 4 months ago, it was a humid rainy day and the RX was running great for about 25 miles to work . The trip home was back to it's crappy self.

Thanks for your help.

 

Possible restricted exhaust system. Either pull the catalytic converter off and inspect or take to a exhaust shop and let them test.

 

OK - thanks - I will give that a shot, also.

Humid morning today - running a little better. I don't know if it the heat or humidity (or neither) that is helping or hurting.