Isn't that pretty much the same as saying, "It works fine, except for the part that's broken?"
I don't have any tips for you, but I'll send your question to a couple of Yeddai who might.
The srping that actuates the impulse drive may be weak or broken.
If it's a single sprayer ona a garden hose as opposed to a complete underground system. Replace it at local Hardware or Garden Center or home improvement center.
If it's on a underground system it will have to be replaced by the same manufacturer, like "RainBird". They are easilly replaced, You MAY have to dig around tehe old one to get to the connection. Just unscrew the bad sprinkler and replace. Make sure you use teflon tape around the threads of the new sprinkler before installing.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them