Lambda and afr on dash not matching

Have a problem with lambda reading being way too high. LSU 4.9 sensor at idle I'm seeing 1.9 lambda it drops a bit when I hit the gas, but my AEM dash is reading afr right. Showing 14 and 13 when adjusting fuel trim. EMU black ecu. Kinda hard for me to tune like this. Any ideas. If I try to make the lambda go low the engine runs rough and will die.

What is the LSU 4.9 sensor connected to? Does that controller use the calibration resistor, or is free-air calibration required? Where are you getting the Lambda reading that is incorrect. How is the wideband controller connected / communicating with the the device you are getting the reading from.

You need to provide a bit more information for someone to be able to help you. You are assuming we know more details about your setup. Often posting configuration files and logged data showing the problem is necessary.

Hi thanks for responding. The sensor is connected to the ECU. The ECU is a ECU Master EMU Black. I don't know about the resistor. I cant seem to find the wide and calibration in the ecu. It has preset options for narrow band, LSU 4.2 and LSU 4.9. Wiring specialties made my wiring harness. That the O2 is plugged into. Is there a way to check that the resistor is installed? When I looking at the ECU lambda data it is 1.9 at idle. My target is .95. I have the 7 inch AEM dash that shows the AFR and it is working. I will get a log and show you what I am seeing on the ecu with pictures of the dash. RB26, 1300cc injectors, ITBs, 42 psi fuel pressure.

First, make sure you really have an LCU 4.9 and not the 4.2 sensor. Notice the wiring is different for the two -- verify the wiring matches what is required. It would be easy to wire with a 4.9 connector, but use the 4.2 pin numbers. The wiring diagram is in the help for the Sensor Setup->Oxygen Sensor window. The wiring diagram shows that they connect to the calibration resistor found in the 4.9 sensor connector (BTW - never remove the sensor connector -- that has the laser-trimmed calibration resistor for that particular sensor embedded). I see no provision in the software to do free-air calibration to compensate for sensor life.

Next make sure the installation of the O2 sensor does not have any air leaks upstream that would cause a lean reading (cracked header, missing gasket, etc).

Yes I did make sure I have a 4.9 sensor. I will verify wiring with multimeter per wiring diagram. I will also check for upstream leaks. It's all v bands so it should be relatively easy to do that. Much appreciated David.

The wiring is good. I finally got the lambda to act right it's just hard to keep it idling. It idles very low. I think I need to adj the timing or something just not right. I have killed my battery cranking it too much. I'll mess with it some more tomorrow.

Well, 26 deg of Ignition timing at 800 RPM doesn't sound right. Have you verified the ECU timing matches what the actual with a timing light?

Jason,

Yup good voltage is important.

As David mentioned, 26 degrees of timing sounds like a lot, so the ECU is perhaps trying to increase speed without sufficient airflow. Adding airflow will likely allow more reasonable ignition advance at idle speed.

Just in case someone else is having the same concern you originally posted about, what was making the ECU report lambda incorrectly?

I am not sure what was causing the initial issue. I am trying different things to get the lambda working properly. I have had it idle smoothe but I havent been able to get my wideband to act right. My fault on that. I am learing a lot as I go and I am doing odd things. First I believe I need to get my base timing set by locking the ignition angle on the ecu at 20. Make sure it's firing at 20 degrees with a timing light. Then unlock it and have my ign table at 20 degress and see if I can get it to fire at 20 then work on the fuel. Does that sound correct? Another problem I have is I dont know what figures to put into the timing collums so I have put 20 degrees in the idle zone (lower 6 blocks). Thanks for the help guys.

Making sure the ECU is firing the coils when it thinks it is, is certainly vital. Setting the base timing offset is something I usually do by cranking the engine without starting it, then confirm it again when I'm ready to start and idle it.

What engine are you working on?

RB26 1300id g35-1050 ECU Master, ITBs, forged bottom end 269 cams. Ti retainer a bunch more mods

Finally I got it working right. I had to set base timing. Then set the timing map to 10 and put the fuel map at 50. Double checked the ign outputs. I had to add more fuel to get it to fire. Warmed it up then I revv it up and made the start of a map. I see it is running a bit lean according to the log. At 3k 3500rpm it was 1.01 to 1.1. I'm learning more everyday. Hope to see you all around for the next hurdle.