I have an 02 Mustang Gt and recently the service engine soon light came on, so I plugged a scanner in and got codes P0171 and P0174. While sitting still the idle will increase just for a couple of seconds and then go back to normal. It does this over and over. Other than this, the car seems to be running ok but it is due to be inspected at DMV. Any help would be appreciated. Thanks
Larry

 

I would personally find out what the codes mean before jumping to any conclusion sometime those codes can help you solve a problem fast and easy.

 

System Lean Bank 1 and Bank 2. Possible vacuum leak, dirty MAF, other causes.

 

I agree with dave. I would check for a cracked, loose or disconnected vacuum hose. Get some carb cleaner and spray all hose connections with the engine running. If you have a leak the cleaner will get sucked into the intake and the idle will change. Also get some mass air flow cleaner and clean yours. This is what I would do first.

 

FWIW you can look up OBD codes online http://www.obd-codes.com/

Suggestion regarding cleaning mass air flow sensor is a good one, computer controlled cars get funny when sensors report wrong

 

Guys I found the problem and it was a vacuum hose. The one that runs underneath the air filter tube was collapsed. Thanks for all your help.