When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So i was on my way to work today. My AFR went from 14.8 (ish) on average when cruising/idle to 17.5-18.0 .... No changes made other than I just got on it a little bit and did a mild pull from 60 to 100... not even real aggressive. I've put about 30 miles on it since winter hibernation. seems to run the smae without issues..... just concerned with the sudden jump after a year
it's a 2006 base, A&A supercharger, long tubes no cats, AEM wideband , BAP on hobbs
I'm going to do a scan and log when I get home, but looking for some input from the forum to help look in the right direction.
could it be wideband sensor starting to fail?
maybe something to do with a vacuum line?
Last edited by hmmmm16417; May 14, 2021 at 09:48 PM.
Reason: Fixed issue
I think youre on the right track. Check for vacuum leaks and anything that may have dry rotted over the winter. If everything looks good, see if your wideband needs an open air calibration, I know some of them you can do that. Also make sure your upstream o2s appear to be functioning normally (although if they werent it would probably throw a check engine light)
Your Vette was sitting for a while as you stated and you probably should do an open air re-calibration of the Wideband O2 Sensor - it could of got moisture on it or anything. It certainly won't hurt to do the re-calibration
Let us know your findings, because a mild pull even at 17.5-18.0 would of given you some knock under Boost and pulling timing (It should be going the other way, into the 12 to 11's AFR during the mild pull and depending on how much Boost and how "rich" it is at WOT could be in the 10's AFR)
Your Vette was sitting for a while as you stated and you probably should do an open air re-calibration of the Wideband O2 Sensor - it could of got moisture on it or anything. It certainly won't hurt to do the re-calibration
Let us know your findings, because a mild pull even at 17.5-18.0 would of given you some knock under Boost and pulling timing (It should be going the other way, into the 12 to 11's AFR during the mild pull and depending on how much Boost and how "rich" it is at WOT could be in the 10's AFR)
Thanks,Matt
will update when I can dig into it. In middle of bathroom remodeling and my son home visiting from military .....and mother nature dropped 6"+ of snow on us lol
will update when I can dig into it. In middle of bathroom remodeling and my son home visiting from military .....and mother nature dropped 6"+ of snow on us lol
Right on
Here is a little something just to help with AFR (even though you are not using this exact product)
Today i had some time to tinker. I cleaned the MAF sensor, used the maf cleaner on O2 sensors ( ot sure if that did anything) , performed a free air calibration of the wideband. (AEM) , and installedfuel pressuregauge - conformed fuel psi @ 60
still idle at 17 ish for afr
guess I need to start checking vacuum and exhaust leaks and do some data logging?
hesitate slightly when stepping on gas, but still runs good under load
Sounds initially like there COULD BE a slight lean tip-in issue in the tune. Hard to diagnose without logs as there are a couple places in the tune a tip-in problem can be. Do you have a tuner?
As MTBSully stated perform a recalibration. I have had a couple of wideband sensors fail in the past, in those instances the wideband read lean. My experience with vacuum leaks have caused high idle speeds.
Sounds initially like there COULD BE a slight lean tip-in issue in the tune. Hard to diagnose without logs as there are a couple places in the tune a tip-in problem can be. Do you have a tuner?
I have HP Tuners ... haven't changed tune , same tune i started with last spring and ran all summer. Will be getting some logs when weather gets better
As MTBSully stated perform a recalibration. I have had a couple of wideband sensors fail in the past, in those instances the wideband read lean. My experience with vacuum leaks have caused high idle speeds.
I did the recalibration with the Wideband out of exhaust, didn't change.
Unless there's a different way to do it other than with the gauge itself?
I did the recalibration with the Wideband out of exhaust, didn't change.
Unless there's a different way to do it other than with the gauge itself?
I wonder if the sensor itself is bad - it does happen
How old is the sensor? the AEM setup?
Are you running Meth? it's not stumbling or running funny or anything like that when it is idling is it?
Have you checked the plugs?
With the tests and cleaning that you have done I am leaning towards the O2 Sensor being bad or going bad, especially since the "Tune" has not been tweaked or touched
Too bad you didn't have someone that has a wideband setup that they can slap on to see what it reads, I also would think that if it were that lean that the PCM would be trying to compensate to richen up the fueling -
Either let the car idle in the driveway or take the car out for a spin, perhaps using cruise control, no need to boost it or get in to PE. I would log the narrowband O2 voltages, duty cycles and log the wideband until after I have recorded the lean condition. Then I would examine the log to determine if there were any significant value changes as the log transitions to the lean condition. If there are not significant changes in the narrowband voltages or duty cycle values, then I would suspect a faulty wideband system, my guess would be the sensor.
Here's a pic of a log with the sensor going bad. Note near the cursor, the Cmd (afr) and the WB O2 (afr) start to diverge. As I recall the sensor false readings were intermittent at first.
I have had my air filter start to slide off my air filter duct/bridge and cause the same thing after a hard pull. make sure your air filter isn't sliding off because it will pull more air if it is.
Here's a pic of a log with the sensor going bad. Note near the cursor, the Cmd (afr) and the WB O2 (afr) start to diverge. As I recall the sensor false readings were intermittent at first.
What model is your AEM?
Time to look or start pricing a new wideband O2 sensor.
Thanks, Matt
Last edited by madmatt9471; Apr 24, 2021 at 03:59 PM.
AFR too lean - RESOLVED!!
