Q: Engine idle fluctuates
When you start the car it idles between 1000 and 3500 rpm's. Up and down. Up and down. After about 5 minutes it then surges to 5000 rpm's and would blow up if I didn't shut it down. I have replaced the iac valve and the map sensor neither of which has helped. I'm stumped. Any suggestions? Thanks
My car has 190000 miles.
My car has a manual transmission.
This may be a sign of a vacuum leak. A vacuum leak can be one of the most frustrating and difficult problems to diagnose. High idle speed is a common sign and stalling is another. Confirmation of an engine vacuum leak can be a very loud hissing sound coming from the engine area. When a vacuum leak is present in an engine, this causes an excessive imbalance in the air/fuel ratio which creates a loss of power and causes the motor to run at a much higher RPM as a result of the increased oxygen present in the fuel charge being injected into the motor. I would recommend having an expert from YourMechanic come to your location to diagnose your vacuum leak as these can be very difficult and time consuming to trace.
Get an instant quote for your car
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing