Cycling Idle RPMs at start

My 1995 Saturn SC2 has a difficult time starting and running. Actually, it starts fine and revs up nicely. But before I can put it into gear and back down the driveway, the engine slows to a stall and will gasp and choke and threaten to die - or will die. If it doesn’t die (I’m very lucky) it will rev up nicely again (~1k RPM) and hold that for a second or two, and then slow down, start wheezing, gasping and threatening to leave me to walk. It will repeat this cycle several times until it finally dies.

Then the real challenge begins - getting the car to start again! I can turn it over with the starter motor, but it doesn’t fire off. I know w fuel injection it is considered bad practice to “pump the gas”, but this seems to be the only thing I can do to get it to catch and fire off again. Once I do, the car will start the cycle of revving and stalling as decsribed earlier.

The problem is much worse when the car is warm. Recently I replaced the Crank Shaft Position Sensor which is known to have problems when the car is warm. It didn’t solve the problem.

When I turn the car on before starting cranking the starter motor, I can hear the fuel pump pressurize the system and then stop, so I believe the fuel pump is ok.

I haven’t changed the plugs for several years :(, or the fuel filter ever… so… is this a “duh”?

You should certainly give it a new fuel filter and probably new plugs and wires but this sounds a lot like a vacuum leak.

Get it running, pop the hood and listen for hisses - it sounds like your leak may be substantial enough that you might just be able to hear it easily. Pay special attention to the big black air tube that runs from your air filter. If you don’t hear anything, take a small piece of hose (anything small and flexible) - stick one end in your ear and fish the other end around the intake tube and then any other vacuum hoses you can find. There should be a schematic of your vacuum system under the hood to help you find it all. The sure-fire way to find a vacuum leak is to have a mechanic do a “smoke test” - probably about $100.