'03 Malibu, 3.1, rough idle and tapping sound, shows misfire and O2 sensor

FIREFIGHTERES755

MEMBER
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!

Wednesday, April 4th, 2012 AT 3:49 PM

4 Replies

HMAC300

MECHANIC
48,601 POSTS

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.

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Wednesday, April 4th, 2012 AT 7:41 PM

FIXITMR

MECHANIC
9,990 POSTS

Do a compression test?

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Wednesday, April 4th, 2012 AT 8:39 PM

FIREFIGHTERES755

MEMBER
1 POST

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!

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Wednesday, April 4th, 2012 AT 9:24 PM

FIXITMR