1999 Escort ZX2
 

Hello,

I have a 1999 ZX2 with about 160000 miles on it. Most of the time when i try to run the heater, the engine will run fine and then surge in a rhythmic manner. I have to be sure to have my foot firmly on the brake pedal because it wants to lurch forward when it surges. This only happens when the heat is turned on. Any ideas of what to check into?

Thanks

I know you would like a definitive answer, but I can only speculate here.
The first thought that comes to mind is , the charging system may be trying to keep up with the additional load placed on the electrical system.
Might be a good idea to check the battery connections and ground connections since there could be a voltage loss in one or more of them.
Also, check the blower motor for excessive draw. If you turn the heat on and disconnect the blower motor does the engine still want to surge?
Last but not least check or have the charging system checked out , it will try to raise the engine RPM in order to maintain the required system voltage.