Toyota Repair: 2001 Corolla Engine Light, fuel pressure gage, intake manifold gasket

Question
Light comes on after about 100 kil. at highway speed when stopped and idled for a couple minutes. Also hard to start again after shut down for five minutes after long drive. Need to give half throttle to start. Fault code is 0171.

Answer
Robert,

This engine code p0171 indicates the engine is running lean or not getting enough gas.  There are several possibilities that can cause it. First, would be a vacuum leak somewhere. Any broken or disconnected vacuum hoses or a leaking intake manifold gasket would count as a vacuum leak.

The second would be low fuel pressure caused by a bad pump or even a clogged fuel filter. You need a good fuel pressure gage to check this so maybe have your mechanic do it.

Last, the oxygen sensor itself could be bad and staying lean all the time.