what to do

[jerry takahashi]

Hi I have a 2000 Corolla with about 127000. The check engine light came on a few months ago and I read the code 0171. I cleaned the Mass Air Flow Sensor and the light and code went out. Then last week the check engine light went on and code 0171 came up again. Then three days later the light went out but now I have code 0300. I checked the plug and they all looked fine. The ignition pack seemed to seal well on the plugs and where all tight. There is no oil leaks or any around the boots.
I am confused on what to look for. I was all set to test the mass air flow sensor. Then the light went off and now i have another code to look at. Anyone ever had this happen?

Thanks

Jerry

 

[mikeyb]

Replace intake gasket and check intake hose. Also replace the throttle body gasket. You're getting too much air from somewhere and the common is the intake gasket if it's never been done. Could be o2 sensor but you'll need a scanner with live data to see if it's working.

 

[Luis0522]

What Mikeyb is recommend can help but also check injectors if you have a clogged or injector not pulsing corrrectly this can cause a misfire and lean codes.