jerking when heater is on

when I have the heater on in my 2000 zx2 you can feel the car jerk intermitently through out all the gears but it's a very small hesitation what is causing this issue any answer will bring me that much closer :shakehead

Dead miss ? The only two systems that are really affected are the cooling system and electrical systems.

My guess is it's probably in need of a tune-up; perhaps too much resistance to spark and the extra load from the blower-motor pushes it over the edge. Rear defog may also place a lot of load on the electrical system. Gap spark plugs and if non-OEM Spark plug wires or if damaged, replace those as well. Clean the battery terminals with baking soda and ensure that are tight with a good connection. Extra, but safely/properly hook up a volt-meter and ensure that the alternator is putting out a good charge voltage. Around 14 volts is normal.

If it's in defrost then the A/C compressor might be cycling on and off.:2cents:

i've tuned up the vehicle the day after i bought it so i'm wondering if it may have something to do with the need of a new valve cover gasket? ****long shot****

If the valve cover gasket is leaking oil onto your spark plugs it could cause enough resistance to make it hesitate/miss out.

If it's in defrost then the A/C compressor might be cycling on and off.:2cents:

My 97..when I bought it (used).. the heater/defroste/ac fan is off and the compressor does not run when the heat/def/Ac switch is off..in the vertical position. In ANY other positon BOTH the fan runs AND the compressor runs. I can feel the load on the engine WHENEVER I move the switch. The load is the same for heat/defrost/A/c. I tend to drive with that switch in the vertical position. When I need more defrost..I turn it on. Ditto for when I need more heat. I leave the fan in the 2nd position. When I have enough defrost/heat..I turn the switch off. I don't think this is the way it is supposed to work..but it has been that way since I bought it.

If it's in defrost then the A/C compressor might be cycling on and off.:2cents:

Good thinking TW. That's likely it; and by the way if it's cycling on/off that much the system is probably low on refridgerant. Make sure a sufficient amount of lubricant is included with that refridgerant refill.

The compressor is really nothing more than a dehumidifier and may be used during the cooler months to take extra humidity out of the air and keep rom fogging up the windows on the inside of the vehicle.

Also and on my own vehicle, the compressor is purposefully designed not to run at or below freezing. I assume it's the same for all vehicles.