- 2007 LS
- about 98k miles
- auto trans

So this morning I decided to run a routine scan with my dongle scanner, and then I saw/noticed that this "command air-fuel equivalence ratio" was red for some reason? Says it's "1:1" but I'm not sure what that means. Because the letters are red I assume that means it's out of spec somehow

While I had the app open I made a recording of my morning commute:

https://drive.google.com/file/d/1lFW...w?usp=drivesdk

Thoughts on what it means?

Car seems to drive fine other than the very first cold-start of the day, during which I notice the engine sputters a little (RPMs dip up and down for a few seconds/the RPM needle seems to "hunt" for a moment) but then it smooths itself out. All subsequent starts throughout the day are fine (...no random sputter or random RPM dips) - it's just that very first cold-start of the day that sometimes has a rough idle right after starting

No codes shown in the scanner besides that generic seatbelt code (B0081-71), but that "random RPM stumble" on the very first cold-start of the day has me wondering

 

I was unable to run that MP4 file. How big is it?

You need to check your app's documentation to see what red text means.

If fuel trim was out of range, you'd see a code.

You cold start symptoms might be low fuel pressure caused by a very slow leak in the fuel pump check valve, or in the fuel line. These cars are notorious for leaks in rusty fuel lines. Do you ever smell fuel outside the car? There is no fuel pressure sensor. You can check fuel pressure with a borrowed fuel pressure gage from a parts store. It should be about 60 psi, and should hold close to that for several minutes. If it doesn't, the loss in pressure overnight is probably delaying building fuel pressure, causing the initial problems, which go away once pressure builds. OR, there is a very slowly leaking leaking injector, which will cause the same pressure problem, plus flood that cylinder.

Or, dirty injectors are causing an excessively lean condition at cold start. Ever used a fuel injector cleaner additive? Where do you by your fuel. (My cars like "Top Tier" fuel, which has better detergent properties than government minimums, and is recommended by GM.)

(You should be able to find the pressure test procedure elsewhere in these forums.)

Does it smoke on the cold startup? If so, please describe quantity, color and smell.

Have you ever used the proper cleaner products on your MAF sensor and throttle body? This is highly recommended and pretty easy to do.

 

If you copy/paste the URL it should work

Not sure what browser you're using, but it works fine on both my Google Chrome browsers

It's a fairly short video around 14 minutes, just shows mostly low-speed driving on sidestreets

EDIT: just in case there's some sort of issue for readers I went ahead and pasted a slightly different URL in the first post, tested it just now and confirmed it works on 3 different browsers (Chrome, Firefox, Edge)

Here it is posted again:

https://drive.google.com/file/d/1lFW...w?usp=drivesdk

 

The A/F ratio should be 14.7:1. The computer "commands" a ratio to achieve that. If you had a choke and it was on the A/F would approach 1:1.
I think in this case it is a bit of data the HHR computer does not provide.
Is the red there after warm up?

 

You need to learn the tools you have.

 

If I was guessing and it's a dual fuel car I'd suggest there is something off in the sensors for that system. I can't imagine what else that message means.

 

Perhaps its shows red because the dongle doesn’t read it.

 

Hmmmmm, after doing some Googling around I found this:

"Air–fuel equivalence ratio, λ (lambda), is the ratio of actual AFR to stoichiometry for a given mixture. λ = 1.0 is at stoichiometry, rich mixtures λ < 1.0, and lean mixtures λ > 1.0."

So it's possible the "1" reading is just normal, not sure why it was showing as red on my scanner though /shrug

From what I'm reading it's just another way of referring to Stoichiometric ratio

I'll try and record a followup video tomorrow morning for a true cold-start, maybe it will act up, maybe it won't

 

Huh. Today I learned that by "air-fuel equivalence ratio" in your app, they just meant lambda. The tuners talk about lambda all the time. I knew what they meant, I just didn't know it had a plain-english description (which, it seems, makes perfect sense.)

I think maybe stoichiometric ratio is different in that it's a ratio of moles, not mass, like "a/f" and lambda.

 

A ratio of moles?