I've got a vacuum leak light on my dash. I've put a code scanner to tell me what part of the system isn’t up. My car also runs at times and won't go past 30 until I turn off my car and let the computer reset it and then it's normal.
Code scanners aren't really going to help you with that. They can tell you if there's a large leak, a small leak, and stuff like that. But, to really find where' the leak is coming from, you will need a dealer-level scan tool and a smoke machine. These are complex tools. You'll generally need a professional mechanic to find that type of leak.
If it won't go past 30 miles per hour, then you've got some serious problem. If I were you, I would have that looked at relatively soon, because that is a pretty serious problem that you've got going on. Have a mechanic take a look with a dealer-level scanner and diagnose your car's problem.
Have a car question? Get free advice from our top-rated mechanics.
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%