If your check engine light is on, you can visit your local auto part store and have them scan your ECU (main computer) for trouble codes. By your description of the poor fuel economy and rough surging idle, it may be one or some of these following components; The IAC valve (idle air control valve), the O2 sensor (oxygen sensor) may be failing, or the fuel filter may also need replacement. If it has been a long time since you have had a common tune up I suggest you look into your spark plugs replaced as well.
A. J. Pierce
If the car is surging that could be the reason for the loss of fuel. Is the problem more pronounced when the a/c is on? How about the engine light, is it on? There are sensors that control the throttle. Sounds to me like you need to take a ride to your mechanic. If you do not have a one, Look at the askpatty.com site for a shop that can analyze this for you.
Once you repair the surging you will save money on gas.
Audra (the auto-motivator)
〉 Answered on Aug 16th, 2010 by Audra Fordin, Owner at Great Bear Auto Shop
There are quite a few things that could be causing your surge and Fuel consumption: a few things to look at are THROTTLE PLATES, MASS AIR FLOW SENSOR,IDLE CONTROL MOTOR and OXYGEN SENSOR!
Have a Fun Day!
〉 Answered on Nov 20th, 2010 by Diane Larson, Owner/Manager at Larson's Service
Hello Georgia- there could be a few things wrong- surging is generally caused by an idle air control valve- fuel economy issues usually relate to a bad MAF sensor O2 sensor or both- hope this helps- thanks Super Girls Auto.
〉 Answered on Nov 20th, 2010 by Laurie Sarno, Co-Owner at Super Girls Auto
Idle issues could be a sensor called the Idle Air Control Valve (IAC). Do you have a check engine light on? This would help diagnose the problem if it sets a code.
As far as poor fuel economy, there could be other sensors causing this or simply a dirty air filter.
If you have a check engine light on, places like Advance Auto will read the code for free. You can then check out the site www.carmd.com to see what the code means before you take it for service. Good luck.
〉 Answered on Nov 20th, 2010 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines