Anyone Else Feel A "miss" In Their 5.3 Ff/afm?

ShoddyHog · August 27, 2009

The first truck I drove had it, and this one does too. I'm positive it is not something mechanical, but not sure what would cause this. A bad pedal position sensor?

No KR going on at the time.

No, it is not AFM kicking in and out.

Gerry

C. Charles Hahn · August 27, 2009

You're married.... so I certainly hope you're not feeling a "miss" in your truck....

Now if you're feeling a "missus" in your truck on the other hand, that's your business....

Seriously though, I've never noticed anything like that. I am a bit curious though, do you have a copy of your stock tune uploaded to the HPT repository, or could you post one here? I'd like to compare it to the stock tune on my truck just for sh!ts 'n giggles....

HawkeyeOC · August 27, 2009

The first truck I drove had it, and this one does too. I'm positive it is not something mechanical, but not sure what would cause this. A bad pedal position sensor?

No KR going on at the time.

No, it is not AFM kicking in and out.

Gerry

Mine has this too sometimes although it's not a flex fuel motor. I have no idea if it's true or not, but I seem to remember reading somewhere in the forums that the computer runs the fuel mixture a little lean at idol for better emissions?

when this happens on my Mustang, I know it's time to replace/tighten wires or plugs

ShoddyHog · August 27, 2009

You're married.... so I certainly hope you're not feeling a "miss" in your truck....

Now if you're feeling a "missus" in your truck on the other hand, that's your business....

Seriously though, I've never noticed anything like that. I am a bit curious though, do you have a copy of your stock tune uploaded to the HPT repository, or could you post one here? I'd like to compare it to the stock tune on my truck just for sh!ts 'n giggles....

He. There's enought room in that truck for more than just feelin'!

Here's my stock tune:

http://www.carbondaleporkdistrict.com/silv...oFFAFMStock.zip

Here's the log where that screen cap was taken. It is at the end of the log:

http://www.carbondaleporkdistrict.com/silv...EndOfTheLog.zip

Config file:

http://www.carbondaleporkdistrict.com/silv...eradoConfig.zip

ShoddyHog · August 27, 2009

Mine has this too sometimes although it's not a flex fuel motor. I have no idea if it's true or not, but I seem to remember reading somewhere in the forums that the computer runs the fuel mixture a little lean at idol for better emissions?
when this happens on my Mustang, I know it's time to replace/tighten wires or plugs

That's actually exactly what it feels like to me...a bad or loose wire or fowling plug. I already checked the wires for proper installation...should throw a multimeter on them. Hell, I've got a spare set of MSDs that'll probably fit.

I'll be taking her in soon anyway, so I'll have them check it. I'm not overly concerned about it...just strange if you look at the log.

The throttle blade is actually vibrating in the throttle body, so something is actually commanding it to do what it is doing...weird.

C. Charles Hahn · August 27, 2009

I have no idea if it's true or not, but I seem to remember reading somewhere in the forums that the computer runs the fuel mixture a little lean at idol for better emissions?

HA! I wish mine ran lean at idle... mine if anything runs RICH at idle... actually most of the time. I can actually smell the raw gas in the exhaust and see the carbon building up on my exhaust tip.

My TBSS (6.0L LS2) had the same problem; it would belch black smoke like a diesel at WOT, and again would put out the raw gas smell from the exhaust. I am/was always religious about running fuel system cleaner through both of them and do/did oil changes a lot sooner than the OLM advises because of it. Dealers have never found anything "wrong" with either of them, according to them that's "just how it runs" and is no big deal.

Curiously though, the 5.3L in our Envoy Denali doesn't run the least bit rich. It's a different 5.3L than the full size trucks get, though; I believe it's an L76 as opposed to the LC9 (still an aluminum block, but no E85).

I really just need to break down and buy a wideband setup to see exactly what I'm dealing with here. I am thoroughly convinced my stock PE and and airflow tables are just totally jacked up.

C. Charles Hahn · August 27, 2009

That's actually exactly what it feels like to me...a bad or loose wire or fowling plug. I already checked the wires for proper installation...should throw a multimeter on them. Hell, I've got a spare set of MSDs that'll probably fit.

I'll be taking her in soon anyway, so I'll have them check it. I'm not overly concerned about it...just strange if you look at the log.

The throttle blade is actually vibrating in the throttle body, so something is actually commanding it to do what it is doing...weird.

If the MSDs are for your LS2 in the goat, I'm about 99.9% certain they'll work fine on your truck; an LS engine is an LS engine as far as how the coil packs are mounted in relation to the plugs.

I take it you ran the truck with the intake detached from the throttle body to see the blade vibrating? That does seem a bit strange.

Thanks for posting that tune; I'll look it over in a bit, should be interesting reading.

ShoddyHog · August 27, 2009

If the MSDs are for your LS2 in the goat, I'm about 99.9% certain they'll work fine on your truck; an LS engine is an LS engine as far as how the coil packs are mounted in relation to the plugs.

I take it you ran the truck with the intake detached from the throttle body to see the blade vibrating? That does seem a bit strange.

Thanks for posting that tune; I'll look it over in a bit, should be interesting reading.

Yeah, the heads are the same, but the coil packs are different. As long as they're long enough, they should work.

What I mean is look at the image I posted. You can see where the throttle itself is being held steady, but the ETC itself is jumping all over...same with the injectors, MAP, delivered Torque, etc.

I need to go back and make sure I'm logging the right throttle PIDs. There's a dozen or so, and they all show something different...be it pedal position, where the throttle blade is commanded, and where it actually is. Something is making it jump all over the place.

I haven't logged for misfires yet either.

Gerry

C. Charles Hahn · August 27, 2009

What I mean is look at the image I posted. You can see where the throttle itself is being held steady, but the ETC itself is jumping all over...same with the injectors, MAP, delivered Torque, etc.

I need to go back and make sure I'm logging the right throttle PIDs. There's a dozen or so, and they all show something different...be it pedal position, where the throttle blade is commanded, and where it actually is. Something is making it jump all over the place.

I haven't logged for misfires yet either.

Gerry

Right.... though every log I've ever done has exhibited the same kind of thing. I just assumed that was "normal" to see at idle, but maybe I've been looking at the wrong parameters all along, too....

Come to think of it, I even saw something similar on a '99 Camaro LS1 I logged, and that isn't ETC equipped...

spikesputnik · August 27, 2009

Yes.

ShoddyHog · August 27, 2009

Right.... though every log I've ever done has exhibited the same kind of thing. I just assumed that was "normal" to see at idle, but maybe I've been looking at the wrong parameters all along, too....

Come to think of it, I even saw something similar on a '99 Camaro LS1 I logged, and that isn't ETC equipped...

Well, I'm not quite so sure I'm making a correct statement. Need to do more logs, but working late tonight on a project.

Just to be sure - the log (image) I posted above is not at idle. All that "vibration" of the Injector Pulse Width, throttle, timing, delivered torque, and MAP is not normal. If you were to look at the logs or when I get a chance, you'll see that it doesn't normally do that...those lines are smooth.

The log I posted (at the very end of it) was the worst of this "miss" I could duplicate...that's why I stopped it where I did, so it would be easy to find. Couldn't duplicate it on the way home from work today.

4wd · August 28, 2009

you mean misfire?

ShoddyHog · August 28, 2009

you mean misfire?

Not sure what you mean. I mean it feels like it has a miss...as in yes, a missfire.

I'm not sure it is actually a misfire though, or some malfunction that feels like it.

Gerry

ShoddyHog · August 28, 2009

you mean misfire?

In other words, it feels like I've pulled a spark plug wire off...but intermittently and only at light to medium throttle.

Gerry

2k8Vmax · August 28, 2009

i noticed the same thing on my 08' V-Max. i thought maybe it was something with the VVT. it seamed to do it mostly on light to medium throttle, on a slight incline. it seamed like when i gave it a little more gas, it would change timing and the "miss" would go away... anyway, with my black bear tune, it seamed to go away for the most part. i notice it every great once in a while, but not like before.