Corolla'00 vibrates and stops. Engine check gies P0171

I bought and drove car since Sept-2005. Absolutely No problems till May-2006.

Then it started showing P0171 but no problems while driving. Then it started vibrating mainly while starting in the morning and very rarely in afternoon again when I leave for lunch. But otherwise it runs sooth at any speed all the time on any road. I have taken it on long drives (500K Miles+) too.

I cleaned MAF sensor wires with CRC QD Electronic Cleaner couple of times, but it has not helped. When I took the car to Toyota dealer, He advised to replace the MAF sensor and both O2 sensors. But its costly affair $600+

Not sure what to do next? Is it related to Vacuum Lines leakage? Where can I check leakages in Vacuum Lines at reasonable cost? Or Should I replace MAF sensor first? Can someone Please Advice!

I'd agree, 500,000 is a long drive!

P0171 means that the system is too lean.

The MAF sensor and O2 sensors affect fuel-air mixture. Why don't you price the MAF sensor and O2 sensors to see what the parts prices are and then change them yourself? For $10/day, you can access the factory service manual at techinfo.toyota.com for instructions on changing these components.

You can also check local salvage years for the MAF sensor although I would not bother with a used O2 sensor.

Another approach is to have the dealer change only the MAF sensor and see if the condition clears up.

A vacuum line leak can cause a rough engine but it is unlikely to cause a lean mixture in your car. A simple vacuum gauge will tell you if there is a vacuum leak but if it were my car, I wouldn't waste the time looking for a vacuum leak.