Hard start especially when warm / hot
1999 Bonneville 3.8L NA 163,000 miles
When the car is cold, there is little problem starting. After the engine warms to operating temp, it is very often difficult to start. It turns over fine, but cranks unusually long, fires a few times, then fires and runs OK.
CEL light is on, P0171, lean condition.
I have replaced the FPR, some bad vacuum lines, spark plugs and the upstream O2 sensor.
I have cleaned the MAF (but have not ruled this out as the problem yet) If I disconnect the MAF while idling there is no change idle quality.
Fuel economy is poor (about 16 MPG) combined driving.
Coolant level remains constant (full)
No drivability issues noticed.
I do know that the plug wires are not in the best of condition, and will replace them at next opportunity.
Can anyone help me pinpoint where the problem lies?