AEM AFR gauge not working

[mender]

I just installed an AEM AFR gauge in the CIvic to allow monitoring and datalogging via the S300. So far, the gauge has worked properly for about 30 seconds from what I can tell.

 

I've been using my LM-1 Innovate wide band up until now for chassis tuning but it's clumsy trying to monitor the hand-held and match that to the rpm during the pull. I don't entirely trust the dyno chassis O2 readings and obviously don't want to go lean. Thus the AEM gauge, but I'm not seeing what I expect from the gauge, specifically a reliable reading.

 

I've tested the gauge and O2 sensor with the sensor in free air by first unplugging the sensor lead and turning the power on. That gives the start-up sequence on the gauge, then a steady 14.7 reading as expected. I then power off, reconnect the sensor lead and power on. Start-up sequence again followed by 14.7 which after a few seconds starts to increase until it goes off the scale with the three bars remaining. I then sprayed brake cleaner on a rag and wrapped the end of the O2 sensor, which was getting moderately warm. The gauge then came back on and the numbers went down until it was reading 10.0. Unwrapped the sensor and the numbers went lean again. 

 

I repeated the brake cleaner/rag test but this time there was no response. I started over from the beginning, unplugging the sensor lead and powering on the gauge with the same result: 14.7 steady. Next step, plugged in the sensor lead and powered on again; 14.7, then increasing until off the scale. Brake cleaner and rag once again, and got the expected response but only once.

 

I installed the O2 sensor in the second bung of the header and compared to my LM-1 as I did laps around my storage compound; got the expected readings from the LM-1 but no response from the AEM (full lean, three bars). Did the scheduled chassis dyno session that evening, again with the LM-1 reading properly and the AEM reading full lean. Did some tuning changes after setting the baseline and lost power, changed back to the baseline and lost more power. There are other things going on but I was really hoping to get the AEM working and the S300 datalogging properly.

 

I called AEM and they had few questions, basically saying that the O2 sensor is faulty and sending me out a replacement. I doubted that it would arrive in time so in the meantime I bought another O2 sensor to test. So far I have the same results with the new O2 sensor (tested last night) so I'm starting to doubt the gauge now.

 

Any thoughts or suggestions? My expectations were that the AFR gauge would mirror my LM-1 under most conditions but so far it seems like money wasted.

Edited August 27, 2021 by mender

[mcoppola]

There is a known problem with the Bosch O2 sensors that AEM uses. 

I called them when mine behaved the same, brand new.  Their instructions were to destroy the sensor by cutting off the wires. Send them pictures of the destroyed sensor, and they will send a new one for free.

The dyno operator also gave me a tip to put the AEM gauge on a switch so that the preheat feature is not on when keying up the vehicle for work when not actually firing it up. His theory was that there's no reason to put the sensor through unneeded heat cycles without proper feed of exhaust gasses.

[mcoppola]

@mender I saw 3 bars on the AEM during our race at times this past weekend, but it was under decel, and it came back on again each time the engine was under load, and has been working fine with the new sensor since we replaced.

The datalogging feature DID work very well. We got good AFR readings on the AEM that were sent along with other data to our "E-tuner" while doing our dyno work.

(P.S. been busy and out of touch, but will talk soon. Good Luck, and thanks a TON for all the engine building advice and tips. People saw your work in action last week!) 

Edited August 27, 2021 by mcoppola

[mender]

The sensor that I just bought is a generic one to replace the Bosch sensor, having read that the Bosch ones were an issue. No change so far from with the original.

 

For the LM-1, the preheat cycle is required before starting the car so interesting that your guy recommended the opposite for the AEM.  I would expect the three bars once the mixture goes past 17:1 on decel but so far I'm getting no response under any conditions. I'll put it together tonight and do some more laps.

 

Glad that at least your car is working well!  

Edited August 27, 2021 by mender

[mcoppola]

9 minutes ago, mender said:

The sensor that I just bought is a generic one to replace the Bosch sensor, having read that the Bosch ones were an issue. No change so far from with the original.

Darn, thought I could return some help....

I would call AEM. Perhaps the generic gauge sensor won't work with their system?

Worth seeing what they have to say...

 

edit: sensor, not gauge

Edited August 27, 2021 by mcoppola

[mender]

1 minute ago, mcoppola said:

Darn, thought I could return some help....

I would call AEM. Perhaps the generic gauge won't work with their system?

Worth seeing what they have to say...

Just got the generic one in the mail yesterday but have house guests so only had time for about 15 minutes at the shop last night under the pretext of checking tire pressure on my wife's vehicle, will try again tonight.  

[thewheelerZ]

Had a similar issue with AEM gauge/sensor.  We thought maybe we knocked the sensor when removing exhaust 9apparently they are fairly sensitive to shocks?).  The rag test worked every time, sensor was getting warm, but would basically go full lean right away on startup.  During this time the buttons on the gauge wouldnt work to try some of the reset calibration and such either.

 

 In any case, we replaced the sensor as the first try at throwing parts/money to fix and it now works as advertised.

[Ian]

I've had nothing but issues with AEM UEGO's.  It's say 50% or more have junk sensors out of the box, and 25% of replacement sensors are also junk.

 

Often the failure mode is as described, fade to full lean regardless of actual o2 content.

 

But to be absolutely sure, I'd recheck wiring.  I've had quite a few units behave strangely when not grounded extremely well.  Even something as simple as a stacked ring terminal at grounding point can freak them out.  I tend to dedicate a ground just for the controller on the cylinder head or block.  This is true of the newer Innovates, Zeitronixs, and AEMs.

[Rodger Coan-Burningham]

15 hours ago, Ian said:

I've had nothing but issues with AEM UEGO's.  It's say 50% or more have junk sensors out of the box, and 25% of replacement sensors are also junk.

 

Often the failure mode is as described, fade to full lean regardless of actual o2 content.

 

But to be absolutely sure, I'd recheck wiring.  I've had quite a few units behave strangely when not grounded extremely well.  Even something as simple as a stacked ring terminal at grounding point can freak them out.  I tend to dedicate a ground just for the controller on the cylinder head or block.  This is true of the newer Innovates, Zeitronixs, and AEMs.

 

As I read thru the thread I was going to ask where the sensor heater ground and sensor signal are grounded, at least in the older AEM units they are separate. When not grounded well or sometimes grounded together can give weird output.  As stated here, most likely just bad sensor but would just check grounds to be sure.

[mender]

Installed the new generic sensor, let my LM-1 go through its preheat cycle and started the car, LM-1 reading matches previous experience, AEM goes to full lean after a few seconds and doesn't return. Try several different start-up procedures with no difference. That's two sensors with the same result, one Bosch and one generic.

 

Will have to go old school and datalog visually via Go-Pro, doing an autocross event today to check suspension settings, axle retention, etc, and of course just for fun.   

 

There's only one ground from the gauge, the sensor heater grounds through that. Sensor signal goes through a white wire to the S300 for datalogging, 0-5 volt and the S300 is tracking that accurately. Checked and cleaned the chassis ground, checked the two engine ground straps, no change. 

 

Edited August 28, 2021 by mender

[mender]

So the autox went pretty well, unfortunately the AFR gauge was still offline - mostly. Several times for 2-3 seconds I saw what looked to be a proper reading. It would go from ful lean to about 13.3 - 13.5 then flash back to full lean.

 

No transition, so I'm thinking a bad/intermittent connection somewhere. 

[mender]

It was a fun autox event, not the least because only six cars showed up! We got quite a few runs today!

 

The car ran well, only had the RF camber adjustment slip, an easy fix. I usually tack the adjustment for races but wanted to be able to change it if needed. The driver had to made some adjustments as well, it's been a few years since my last autox event. Once the tires were up to temp, the car was predictable and tossable. 

 

I didn't quite get FTD, that went to a Cayman GTS on Falken RT660 tires. Their best time: 54.33 seconds (nice fast/open course); my best time was 54.71 seconds. Should have put the new tires on, the ones I used were last year's Area 27 R-S4s.

Edited August 29, 2021 by mender

[mender]

Any suggestions for a reasonably priced UEGO gauge that works? I may have fried this one, or at least fried what looks like a surface mount mosfet in the gauge by accidentally crossing two sensor wires while testing the wiring. 

 

I'd like to repair the gauge by replacing the damaged component but can't read the part numbers. Looks like D1100 with N303LL underneath but the burn spot is obscuring the last couple of digits of each. Any hardware guy recognize the designation? I'll try to get a picture. 

[mender]

Just ordered an Innovate gauge, my old LM-1 still works fine so hopefully their AFR gauge will be as reliable. 

 

Still going to see about repairing the AEM gauge if anyone can help me with that part number. 

[QuaTTro]

42 minutes ago, mender said:

Just ordered an Innovate gauge, my old LM-1 still works fine so hopefully their AFR gauge will be as reliable. 

 

Still going to see about repairing the AEM gauge if anyone can help me with that part number. 

We've been using the Innovate wideband for a few years and it's working good.  Typically we run it's calibration process before each race weekend to be sure it's accurate.

[mender]

Just installed the Innovate LC-2 and it works!

[mender]

Another update: did some laps around my storage facility with datalogging, and the LC-2 is working nicely. I have a track session on Monday so hoping to get some datalogging at race speeds and maybe even some fine tuning!

 

[mhr650]

1 hour ago, mender said:

Another update: did some laps around my storage facility with datalogging, and the LC-2 is working nicely. I have a track session on Monday so hoping to get some datalogging at race speeds and maybe even some fine tuning!

 

I have 2 LC-2's, one for each rotor. I was impressed with how sensitive they are. At one point I had a setting wrong and wasn't firing the leading plug on the rear rotor. It showed the rear rotor lean but getting closer as rpm went up and the leading to trailing split went down.