Rough running

[Billy Mild]

I still have the slight backfire in the exhaust when coasting to a stop and in gear.

I had a few hesitations today when at a lower speed and going 25-50% throttle. It almost cut out. I do now have some datalogs. I'm not sure how to look at what is going on from the logs?

I noticed BLM when at part throttle are NEVER at 128. They are always at 125-112. That seems rich, but would O2 sensors affect this reading?

[BigJohn]

So that's what that is called!

[Billy Mild]

Is there anyway to upload my catalogs?

Sent from my Nexus 6 using ZR-1 Net Registry mobile app

[XfireZ51]

Originally Posted by Billy Mild

I still have the slight backfire in the exhaust when coasting to a stop and in gear.

I had a few hesitations today when at a lower speed and going 25-50% throttle. It almost cut out. I do now have some datalogs. I'm not sure how to look at what is going on from the logs?

I noticed BLM when at part throttle are NEVER at 128. They are always at 125-112. That seems rich, but would O2 sensors affect this reading?

The BLMs are indicating what the O2 sensors are reporting over the long term.
Difficult if not impossible to always get 128s. Depends on the time and gas u want to burn. Acceptable BLMs range 128 +/- 6. The tighter the better. Also, there will definitely be a disparity between left and right banks. Typically left runs leaner than right side particularly at idle. At PT cruise, it tightens up.
On the backfire, has your calibration disabled Decel Fuel Cutoff? Its also a function of the amount of fuel in the runoff or decel area of the VE(fuel) tables.

[Billy Mild]

XFireZ51, I have a Marc Haibeck tune in my car. Anti backfire mode is enabled as well as extra fueling for the headers I have on my car.

Before swapping headers the car ran soo smooth. I'm wondering if this is all due to the new O2 sensors I installed in the car at the time of the header swap. I didn't make near as much power on the dyno that I would expect from a tuned header car and it occasionally stumbles at part throttle. I have changed the plugs and for the most part it doesn't feel like an ignition misfire.

I will try to do some more datalogging, but my battery needs to be replaced. This is the second time it has gone dead over night.

[XfireZ51]

Marc has stated before that the stock tune on an LT5 is a bit on the rich side, so the addition of headers will lean things out a bit to the better. However, an "out of the box" tune is not likely to be optimized for each individual motor and config. Most "tunes" focus on WOT, whereas part throttle, cruise, idle is a whole 'nother matter.
Frankly, I would not suspect the O2s unless you see something in the datalogs showing signal dropout or a lazy/poisoned O2. The ECM has a very limited range of accommodating some changes but its not "autotune". Especially the OBD1 versions.

BTW, make sure the exhaust has no leaks. High vacuum on decel will suck in fresh air and ignite unburned fuel mixture causing a backfire. The presence of fresh air will also signal a lean condition to the ECM by the O2s and so causing the ECM to add fuel. So if DFCO is disabled, ECM keeps adding fuel.

[Billy Mild]

I ordered a tune from Marc for post header install. I installed the chip before I had the headers put on and it ran great.

A few weeks after the headers this crap started up that I really noticed.

[Billy Mild]

Replaced the battery and the car fires right up.

I did some more ALDLDroid datalogging today. I noticed that when I had the hesitation, it was after slowing down to a stop then getting back on the throttle. The LEFT INTEGRATOR signal was down in the low 80's. I have the datalog files if anyone would like to review them. I don't even know how to open them on my PC.

I would like to thank everyone up to this point.

[XfireZ51]

Originally Posted by Billy Mild

Replaced the battery and the car fires right up.

I did some more ALDLDroid datalogging today. I noticed that when I had the hesitation, it was after slowing down to a stop then getting back on the throttle. The LEFT INTEGRATOR signal was down in the low 80's. I have the datalog files if anyone would like to review them. I don't even know how to open them on my PC.

I would like to thank everyone up to this point.

If you can ship them as a .csv file, I can review it.

[Billy Mild]

https://www.dropbox.com/sh/cln5qzfq0...s4G9dmFxa?dl=0

Here is a dropbox link with the most recent ALDL Datalog. I used the "Mark Datalog" feature, but I'm not sure what that means.