Any suggestions on why my car will surge with the heat on?

I noticed it about a week ago and it stopped. It started again a couple days ago. I have only tried it with defrost on and it seems like the motor is dieing and catching back up?

It doesn’t seem to do it as much when I step in to it? Any thoughts?

Thanks
-Tony

 

In the DEFROST position, the A/C compressor is allowed to cycle on to help dehumidify the incoming air before it is heated. You may be noticing the engine idle RPM being affected by the cycling of the A/C compressor.

 

i was aware of a small surge but this is about a 400-700rpm surge. I have never had this excessive surge when in defrost.

-Tony

 

Yes, that does seem excessive. Is the IAC functioning? Air passages clean?

 

umm not to sure.. it has stoped as of the last two times i drove it.. wierd.. ill check all the air and the heater vacume lines to see if its the problm.. hmm.. wonder if the compressor is locking up and letting go.. ill look in to that next time it surges.. if any one has seen this lemme know..

thanks
-Tony

 

Definitely check the heating/AC system vac lines. Since the direction the air flows is controlled by vacuum, a bad line could be being "called" and causing a vac leak on ya.....

 

thanks for the sudg.. i will check it out..

_T