jtr459

Hi I have a 2010 chevy hhr the Catalytic Converter pipe cracked at the manifold car ran fine but loud I replaced pipe with a new gm pipe on road test check engine light came on po171 and p0300 lean fuel and miss fire runs real ruff black smoke ou the exhaust check for vacuum leaks could not find any I replaced the down stream 02 sensor same then replaced spark plugs same cleaned grounds removed pipe after new cat same anybody have this problem

whopper

It's p0171, not po171 - and that points to the upstream O2 sensor.

donbrew

Or a vac leak from the EVAP solenoid. Among other things.

Why is this in the lounge?

843de

Not in the Lounge anymore Don, and aboard jtr459!

mrarff

OP get a scanner, and a code sheet. This will prove most valuable for any car you own!

Oldblue

Welcome to the site, check the electrical connector for the upstream O2 sensor for loose or damaged or yes even a forgot to connect it connection.