P0171 2006 Saturn Vue - Black Smoke Coming from Exhaust

Question

I have a Saturn Vue 2006.

I'm getting a P0171 code and I'm not sure what the problem is. Could it be the engine control module (ECM) that needs to be replaced? Or do I need to replace the fuel pump or fuel injection system?

Symptom: The vehicle would jerk constantly while at a stoplight or at a stand still after warming the car up. When I would drive, it didn't jerk but there was black smoke coming from the exhaust. Now that we replaced the O2 sensors, the jerking has subsided but the black exhaust smoke is still present when accelerating or driving over 50 mpg. Any ideas?

Answer 1

P0171 Fuel trim system lean

A lot of fuel being wasted, Yes the 02 can see excessive fuel being used as a lean condition, black smoke is more of a mechanical condition, you can expect the sparkplugs to be fouled, and because this vehicle is a drive by wire (no throttle cable) you can expect a P2135 with a reduce engine mode to occur.and worste yet a plugged exhaust system. What can cause this black smoke are coolant temperature sensor , a MAP sensor , fuel soak charcoal canister ,and the ignition coil. a fuel injector that is stayin in the open position. The best start is to remove the sparkplug clean them out, reinstall then test drive and recheck the sparkplug condition and note which cylinder the fouled plugs came from. what you are going to look for is a constantly wet sparkplug, it can be from fuel injector to low compression.