ECU claiming 19.1 AFR, Motor idling normal though

[6Bolt123]

Car: Mitsubishi Eclipse GSX (1995)
Engine: 6-bolt swap with a few extras (AIT, 1600cc injectors, E85 fuel)
EMS: AEM (first generation - silver box)
Wideband: AEM Inline Uego Controller
Problem: Start the car up, ECU shows AFR 14.7 for about 10 seconds then immediately goes to 18.5 to 19.1. Laptop and AFR gauge are both showing identical numbers (makes sense since signal is coming from same ECU pin). The car is still idling correctly though; no back firing or any indication that the motor is leaned way out.
What I tried:
1. I swapped out the 02 sensor for a new (Yes, I have multiple 02 sensors just laying around) one, same issue.
2. I checked the 02 sensor with the “Rag Method.” Both work correctly
3. Moved 02 sensor from in front of my straight pipe (No Cat) to where the original front 02 sensor was located, same results.
4. AEM Inline Uego Controller seems to be working properly (solid green indicator lights = working correctly)
5. Visual inspection of exhaust manifold, turbo, downpipe, etc for cracks
6. Listened for anything out of the norm under/on the motor, sounds normal

What I think:
1. Exhaust leak?
2. AEM ECU issue?
Has anyone had a similar issue? Any suggestions would be much appreciated

 

[jtmcinder]

I would be checking fuel-delivery next.

 

[Jafro]

I've had a similar issue before. I spent 2 years tuning for 14.7:1 because I didn't set the values for my 550cc injectors in DSMlink by right+clicking the A/F value and entering my injector size. I was using a 2003 PowerBook with v2, and failed to Control+click (that trackpad only had one click button). Didn't even know there were options beyond those values that I could set.

Apparently, the ECU sees the sensor's signal and calculates the value based on what injectors YOU tell it you're running. It doesn't instinctively know. My car ran perfectly despite it having the stock 450cc values set. It just displayed an incorrectly calculated AFR.

Perhaps AEM has a section somewhere where you could verify this value? I haven't used that product yet, but it sounds like the same thing I was experiencing in Link. It's not a definitive suggestion that fixes your problem but maybe there's something in there that can help your thought process.

 

[6Bolt123]

I've had a similar issue before. I spent 2 years tuning for 14.7:1 because I didn't set the values for my 550cc injectors in DSMlink by right+clicking the A/F value and entering my injector size. I was using a 2003 PowerBook with v2, and failed to Control+click (that trackpad only had one click button). Didn't even know there were options beyond those values that I could set.

Apparently, the ECU sees the sensor's signal and calculates the value based on what injectors YOU tell it you're running. It doesn't instinctively know. My car ran perfectly despite it having the stock 450cc values set. It just displayed an incorrectly calculated AFR.

Perhaps AEM has a section somewhere where you could verify this value? I haven't used that product yet, but it sounds like the same thing I was experiencing in Link. It's not a definitive suggestion that fixes your problem but maybe there's something in there that can help your thought process.

I was going to call AEM today and see what their techs had to say about it.