i have a 2000 civic lx with the stock y7, its done this since i bought the car and now that we are in the winter i always have the heat on and if its on while the car is idling the whole car starts to shake like its miss firing or like its gonna stall on me. then when i turn the heat off the car goes back to normal smooth idle. is this normal? it happens in the summer with the a/c also

 

it sounds like the electric load sensor is bad. or the fan motor could just be bad and drawing too many amps. idle controller could be bad or dirty, and thus it cant supply more air when theres a load on the engine. or the alternator could be going out.

clean the IACV first if that doesnt help, change the load sensor (its part of the underhood fuse box). if that still doesnt help test the fan motors resistance (should be zero continuity). if it checks out, pull the alternator and have it tested.