When I turn my heater/ac controls on the car will somtimes start surging and run almost like there is a fuel delivery problem. It only happens when the controls are on.

The only thing that comes to mind is vaccum related. has anyone else had this problem.

 

Bad sensor maybe. It is fuel injected right?

 

Well I can't see what sensor would interact with my heater controls but maybe I am stupid.

 

I could be the stupid one, but it was just a suggestion to look at.
Ya never know.DUECE

 

Could it be an a/c system problem causing the compressor clutch to cycle too often? Just a thought.

 

I thought of that and unplugged the clutch and it still does it. It does it on all settings as well. I think the ac is active on defrost and ac. it will do it with the thing set to vent as well. I feel like a complete moron I am stumped.

 

OK, good troubleshooting so far, what year is this?
You're right on about the ac vs vent deal. What about the fuel filter or in-tank pickup. The only times I've had that problem where a semi-plugged fuel filter, bad O2 sensor, and a vac leak.

 

well it is a 90 350 tpi. I have not worried about the fuel supply as the car runs fine until I switch the heater on. If it was a fuel issue my logic tells me the problem would be all the time unless I am missing something.

I can be driving down the road with the heater on and the car surging then turn off the heater and intantly the car runs perfectly.

 

I agree with your logic. That leaves you with the vac. operated heater controls and associated parts.