-LTFT & White Spark Plugs...bad O2?

[tb30570]

working on a 1999 Chev Lumina 3.1L

Has a surging idle in closed loop.
Doesn't surge in open loop or while driving.

Used carb cleaner method to check for vacuum leaks and didn't find any
LTFT is close to -10 (rich)
Spark plugs are white (lean)

If the O2 sensor is indicating rich but the spark plugs say lean, do you think the O2 sensor is bad? ...O2 sensor has switching output voltage

[Tech II]

How is the O2 sensor indicating rich, if it is switching?

The vehicle isn't in closed loop while driving?

Checked for an exhaust leak near pipe/ex manifold?

If you have a misfire, there is more O2 in the exhaust which will cause the PCM to make the mixture rich.....

[tb30570]

Originally Posted by Tech II

How is the O2 sensor indicating rich, if it is switching?

The vehicle isn't in closed loop while driving?

Checked for an exhaust leak near pipe/ex manifold?

If you have a misfire, there is more O2 in the exhaust which will cause the PCM to make the mixture rich.....

Ltft is -10 at idle based on o2 output which indicates the pcm thinks there is less o2 in the exhaust which causes the pcm to make the mixture lean. Based on the spark plugs, data the pcm is getting is false.

The engine goes into closed loop while driving but ltft is close to zero while driving.

My guess is either an injector is leaking or the o2 sensor is bad. If an injector was leaking, the plug for that cylinder should be black instead of white....all the plugs were white. That makes me think the o2 sensor is bad.

[j cAT]

burning coolant !

[tb30570]

Originally Posted by j cAT

burning coolant !

Intake gasket?