Mechanics

'03 , 3.1, ROUGH IDLE AND TAPPING SOUND, SHOWS MISFIRE AND O2 SENSOR

2003 Chevrolet Malibu • 115,500 miles

Today, the car suddenly started running rough and makes a tapping noise. Accelerating seems to smooth out the roughness, but not the noise. Noise seems to be coming from under the intake right about in the middle. Engine scan revealed a "Cylinder 6 Misfire" and O2 sensor.

- Checked #6 plug, it was clean. Regapped to.060 and reinstalled.
- Removed coil pack and inspected. No cracks, produces spark
- Plug wires are new, power does go to the plug
- Good fuel pressure
- Not using (burning) coolant, no apparent air leaks

Now I'm stumped!
Avatar
Firefighteres755
April 4, 2012.



Check your fuel pressure and you may have a lifter going bad on itmaking the noise. We can't hear it so can't really diagnose it.

Hmac300
Apr 4, 2012.
Do a compression test?

Tiny
Fixitmr
Apr 4, 2012.
No, I didn't do a compression test on it. It does sound like a lifter ticking, but without removing the intake manifold I couldn't tell.

When this happened, my wife was driving, came to a 4-way stop, and it started as she was taking off. At that time is when it started running rough and making the tapping noise and the check engine light started.

The plugs were in good shape. Like new, as well as the cables. Coil packs were in good shape, and there was good spark. All the hoses seemd to be good, and no evidence of any air or coolant leaks.

Thank you for your answers!

Tiny
Firefighteres755
Apr 4, 2012.
Maybe a valve spring broke? Might as well pop cover and look things over?

Tiny
Fixitmr
Apr 5, 2012.