Any one else experience this?
I bought 2001 corolla CE Jan 2006.
By May the Check Engine Light came on.
Too Lean fault, First Mechanic diagnosed bad gas, cleared fault, ok for about a week.
CEL back on, noticed performance issues, especially in first gear (manual trans).
Second Mechanic diagnosed bad O2 sensor, replaced it, running worse after, he didn't charge me labour.
I noticed in cold weather worked better than in hot.
Third mechanic did fuel system flush and mentioned that he cleaned the Mass Airflow sensor.
Car running better for about a week, CEL comes back on.
By Sept , days are cooler, car running better, by winter no problems.
This year in May CEL comes on.
I find on internet that this is a commonly misdiagnosed problem with dirty MAF.
2 screws attach it to the air box. Took it off and the two tiny sensor components were all crudded up. Cleaned with electrical component/contact spray cleaner.
Car immediately came back to life, full performance. CEL went out by itself overnight.
If there is interest I can probably find the link I stumbled on.
Hopefully can help somebody,
Brian.
EDIT: See you guys have
been there done that.
The MAF uses 'thermal dispersion' principle.
One of the little electrical components is a heater element, the other beside it is a heat sensing device.
The more air that flows between them the less thermal energy is transferred. An inversly proportional relationship that the computer can use to maintain fuel/air ratio.
If they get gummed up it takes longer for the thermal information to pass because they are thermally insulated.
This causes sluggish fuel response to increasing throttle, causing more air than fuel, therefore poor performance, "System Too Lean". Voila.
It seems simple when you know!
P0171 System Too Lean fault caused by dirty MAF sensor.
Linear Mode
