The car, '85 GS 12A completely stock except for RB muffler. 156K on ODO.

Starts just fine.
Idles a little low.

(here's the issue)
Just as I press on the gas the engine will stumble and sputter.

At cruising and acceleration she seems fine.
On deceleration some popping can be heard coming out the tail pipe.

I know it's time for a tune up, but what specifically should I be looking for in regards to the low rpm stumble?

At her present age, I'm worried that the rats nest will degrade and contribute drive-ability problems. And the inability to source a working ACV has made conventional smogging techniques impractical. For years I've been considering pulling the trigger and getting away from the stock engine set up. At least she's got a GSL rear and full RB suspension. Does it sound like I'm looking for an excuse?

 

Accelerator pump

 

Why is it idling low? Can you not adjust the idle up to 750 with the idle adjust screw? Remove the top of the air box and look down the barrels of the carb. Each time the accelerator is pushed you should see two small streams of gas coming from the acc pump nozzle into the primary (smaller) barrels.


How to check acc pump and idle/mixture from the 79-85 Carb manual.

 

I wouldn't worry about being able to stop the fuel by putting your finger over it, the pump only puts out about 2 psi.

Take a good look around for vacuum leaks. And a tuneup would also be in order (cap, rotor, plugs, wires). I would also check the timing if you suspect it might have been tampered with.




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