Sputter at idle, battery meter drops

[2005TB]

Ok, I'm at work so no tools or anything. So I'm hoping to get some responses tonight so that in the morning I know just what to look for.

Details: totally stock 2005 4.2l 4wd 109,000

JUST had oil change done 100 miles ago.

Driving to work, truck ran perfectly fine. But when I came to a stoplight I noticed this ever so slight "sputter" every 4-5 seconds. It wasn't long enough to drop the RPMs at all, but while gazing over all my gauges, I noticed that when it sputters my batter meter drops a bit then back to normal. This happens every single sputter without fail.

First thing that popped into my mind was alternator.

What do you guru's think?

P.s I did a quick search but unless someone has the same issue hidden in a thread, I couldn't find it

[fishsticks]

You either need to clean your throttle body, or you have the mystery "miss" at idle that a number of us have.

Probably the former.

[2005TB]

Ill do the throttle body definitely. At the same time I'm going to do the plugs since ill have the resonator out of the way anyways. Maybe grab a new air filter once I take a look at my current one. Ill post pictures of how the throttle body looks

[2005TB]

Donny you're always the first to throw a helpful answer I realt do appreciate it!

Anyone have any yays or nays to seafoam?

[JorDaneeKey]

We've used it on every car we've owned. Never had a problem, and in most cases it works really well.

[Conner299]

There's a pretty good throttle body cleaning video on YouTube, put up by MAYO3LT, if you're in need of a quick refresher. Can't get to my computer at the moment, or I'd embed it in the post.

[2005TB]

Already watched it but thanks!

[Trail X]

...or you have the mystery "miss" at idle that a number of us have.

We need to make a club. Misfires Anonymous...

[navigator]

my Suburban(5.3L) has one that is a little more pronounced than my TB (I6)
After doing some research it appears pretty common and is something related to get the right fuel/air mix at idle for EPA stuff.
My Suburban was originally from Wa and has the Active Fuel Management system.
I wonder if it is the same thing for our I6.
If that was the case though I would think the folks with PCM tunes wouldn't have the issue.

[2005TB]

Well. Hubby cleaned the throttle body (definitely needed it, pics uploading)

Reset the PCM by the fuses for an hour. Then let the truck run for a good 20 minutes.

During that 20, it idled perfect.. then we decided to take it for a spin, and once you see the pictures of the TB you'll know why I say you can DEFINITELY feel a difference. But when we got back to the driveway he came to a stop (leaving it in drive) and it started to sputter again. This time it was off pattern though, like every 2 seconds then a 5 second pause then 3 times with about 2 seconds in between, then a pause.

[2005TB]

Alright, here are the pictures:

Right when we took it off:



And after cleaning it, only took about 5minutes or so with the TB Cleaner:

[fishsticks]

Do you have a camera with a good audio recorder on it? Could you take a video of the truck idling?

Get video from the engine compartment and also go around the tailpipe and record there.

(Did you disconnect the battery again?)

[2005TB]

Ha, just got a new DSLR with video so yes, yes I can.

We never disconnected the battery, just pulled both PCM fuses. (Should we disconnect the battery?)

And a thought, we've only listened to/saw the idle from the drivers/passenger seat. Never listened to it from outside the vehicle..

I'll get the video as soon as we can

[2005TB]

Haven't gotten the video yet, but we went out to eat last night an drove a good 45 minutes there and then some shopping afterwards. It started to act better and better an by the time we got home we couldn't get it to touch idle anymore. So we'll keep an eye on it but hopefully driving more will help relearn

[Trail X]

If yours is like mine, it will come and go.

Does anyone else with the phantom misfire have a scangauge? If so, when you watch the AFR reading, is it static at 14.6? I'm beginning to suspect my O2 sensors - because my AFR metric never varies from 14.6. But I'm not sure if maybe the scaugauge is just erroneously reading a set value in the PCM.

But I'm also worried that if I change out my O2 sensors that I'll end up having an SAI issue - because I haven't heard the hairdrier in years. Might be better off just keeping the old O2 sensors...

[RyansTBLS]

Gotta love the phantom misfire, I had it awhile back and my mechanic figured out it was an injector, looking it up it said trailblazers had issues with the injectors, but it wasn't clear at what percentage. For example if 1-10 is bad, then some people wouldn't have problem at all, and others would have to replace the one. We replaced the one, and if we got it on another injector, he recommended doing all the other 5 at once to save on labor. She hasn't thrown any other codes and seems to be fine, though any vibration makes me nervous now.

[The Roadie]

JD, I think you're looking at commanded AFR, which won't change. You should be able to look at raw sensor data with Torque, if not the Scangauge (I forget, now I have Torque)

[fishsticks]

If yours is like mine, it will come and go.

Does anyone else with the phantom misfire have a scangauge? If so, when you watch the AFR reading, is it static at 14.6? I'm beginning to suspect my O2 sensors - because my AFR metric never varies from 14.6. But I'm not sure if maybe the scaugauge is just erroneously reading a set value in the PCM.

But I'm also worried that if I change out my O2 sensors that I'll end up having an SAI issue - because I haven't heard the hairdrier in years. Might be better off just keeping the old O2 sensors...

I've watched it in torque. I can watch the misfire count on cylinder 2 increase at idle.

I have 6 new injectors on hand, just need to tear the intake off.

[Trail X]

See, that's what I was wondering, if I was seeing a command value. I looked into it, and there are x gauges for raw o2 readings, but the response time of any gauge reading other than an oscilloscope apparently isn't much more than a very rough approximation of the o2s response.

I had also misunderstood the way 02s work. Apparently its basically a physical impossibility that they get stuck on a set value. Anyways, the recommended change interval is 100k, because the response time of the sensor begins to decrease. So, I'm saying it could possibly still be a factor in our idle misfires.

[2005TB]

The part that confuses me (other than everything you guys are saying so far) is why it only does it while stopped, in drive. If the truck is in park it idles perfect.. But as soon as I pop it into gear but don't move it sputters. When I come to a stop sign/light, it sputters..