RPM not constant at red lights ?

[sekler]

Hey guys !

my car is in good shape, it's a '92 SVX with 212K km, transmission was rebuilt at 160K

My question is, since I got the car (6 months), when I'm at a red light or just letting the car go forward by itself without stepping on the gas pedal, sometimes still pretty often, it seems that the rpm isn't constant, it fluctuates between let's say 300rpm and 850rpm, making the car kinda trembling at longer stops or it makes it kinda "hesitate" if I don't give some gas for example when I'm parking.

This seems to be only present when I'm going forward and it's especially annoying when I leave from a red light, that kinda fluctuation makes that the car doesn't jump forward on the road smoothly, just when it starts going over 1000rpm all is pretty much ok. I get overrun by toyota echos because of this

Today, for the first time ever, the car's rpm went so low it friggin stopped ! I started back and it's been ok ever since, still doing the problem in the usual variation.

Could it be a clogged up injector ?
I think it may be an overall problem, cause some days the car runs great, and othertimes it seems to not shift smoothly, especially when the car is cold from a start.

thanks !