Sputter at idle, battery meter drops

[2005TB]

Well, I don't know what route to take here.. Tonight it was acting real bad. Instead of sputtering every few seconds, it was a continuous sputter and shaking. I'm clueless an don't want to throw a bunch of money and unknowns. I hate these situations

[The Roadie]

The erratic idle that you can see the RPM drop on the tach, and the voltmeter dip, was probably taken care of by the throttle body cleaning.

In most of our minds, "sputtering" means a misfire. In case you have the OTHER major odd cause of vibration, you might have bad/collapsed motor mounts. This issue has been discussed a LOT on gmtnation.com (not so much here), but it's a 10 Hz rotational vibration that can't be seen on the tach, goes away in neutral and comes back with e vengeance in drive, and is often (not not always) worse when cold instead of warmed up. Observe the driver's side intake manifold plastic with somebody else in the driver's seat, and see if the engine rotates more when it's in DRIVE than NEUTRAL. If so - motor mounts. It's a magic cure that I needed and was highly skeptical of for a long time. Engineering-wise, I now understand the reason to be a rotational resonant vibration due to the coupled mass of the engine/tranny/driveline/diff gears/axles that is different in neutral.

[2005TB]

Ok well now I'm super confused because it does everything you said about the 10hz vibration(ie: worse when cold, when in gear not in neutral)

BUT, it is visible on the gauges.. The tach and volts still dip when it happens

[navigator]

they are both pretty common, maybe you have both issues?

[2005TB]

Apparently haha.

[chevycrew]

The gauges drop because the RPM lowers during the misfire, which in turn causes the alternator to put out less voltage.

Mileage? condition of spark plugs? fuel filter?

[The Roadie]

Ok well now I'm super confused because it does everything you said about the 10hz vibration(ie: worse when cold, when in gear not in neutral)

BUT, it is visible on the gauges.. The tach and volts still dip when it happens

If you can detect anything dipping, you have two problems. Let me know about the amplitude of the rotational vibration.

[2005TB]

110k but we've only had it for 8k. The dealer when we bought it "assured us" that 100k maintainance was done, but no paperwork showing that. We're already in the works of getting everything set for a real 100k maintainance, because we don't test dealers word. We knew that from the get go. Wish I had gotten plugs when we did the TB coulda just done it at the same time.

[2005TB]

Ok Bill, We both have the morning off tomorrow, so we will both go out and watch the intake manifold plastics you mentioned. I will try and get a video as wee to see if maybe we think its normal, but you might not.

I'll also take a video of the gauges to show you whats happening in there.

Thanks for the help guys much appreciated!