So, I'm getting an engine code 0171: system adaptive fuel too lean. And I don't know what that means. I just had my 2000 4runner tuned up, replacing the plugs, wires, and one ignition coil that was bad. Fixed a lot of my issues, but this popped up.

The shop suggested replacing the O2 sensor, and it might fix the code. Not sure that believe that. But it's something else I could do myself.

Any thoughts from the knowledgable forum on a way to fix the code issue? I have Georgia emissions coming up very soon, and it WILL fail if I have any engine codes.

 

Try cleaning the mass air flow sensor. I've seen quite a few get fuzz and dust built up on them, making them give false readings and thus a check engine lit.

 

Ok. Still need a little more help please. What I've done. the plugs, replaced the fuel filter. Cleaned the maf. I've not seen any o2 sensor codes. Any other thoughts?

Edit: removed text that shouldn't have been there.

 

Check for any loose or cracked vacuum lines, including the air intake flexible tube to the throttle body.

Air cleaner in good shape?

 

My '99 FSM lists other possible 'trouble areas' that could cause this:

loose air intake hose
fuel line pressure
injector blockage
coolant temp sensor
gas leakage on exhaust system

Not sure what the last one means

 

Used half a can of brake cleaner. Couldn't find any leaks in the vacuum system.

And the air filter is pretty new.

 

Take the intake flexible tube off and give the ribs on the bottom side a good inspection. It's tough to get brake cleaner, etc. on the bottom side.

Are all the plug boots on tight? Check all the other electrical connections too.