In the Holley forum many speak about a problem with the afr reading. From one day to another it goes up to 35.6 and stays there. With closed loop its flooding the engine. A new WBO2 Sensor doesn't help. Now i am at the same point, using the "Email A Technician" function at the Holley site a month ago, no reaction. Tried to register at the Holley forum two times, got only the first email to confirm my email-adress, but never the second notification that i can make a post there. Did someone have the same problem here? how expensive was the repair ?
If I'm reading your post correctly, the ecm is trying to add 35.6% fuel? If this is correct, I'd check for vacuum leaks, especially check vacuum at map sensor. What does the map sensor voltage read? Possibly a bad map sensor.
What your experiencing could be as simple as an exhaust leak. A leak before or within 18” after the O2 sensor will give you issues
Mine did that several times during my 400 mile trip to Waterboys house and back. It eventually left me stranded on the side of the highway 100 miles from home. It seemed to do it more when hot. Never isolated the exact cause. Holley checked out the unit and said there was no faults in the ECM. To make corrections I first re wired the main power supply as per Holley's instructions. Then made up new plug wires and routed them as far away from the TB as possible. Replaced the o2 sensor with a Bosch unit. Then relocated the coil to the firewall. So far so good. After it was running again I had a good tune done on the fuel curve and timing.
Even though they give that clamp on o2 sensor bung.....this is huge source of issue, use a true weld in part
I started the car and all values at the display where ok, but then the afr go up to 35,6, maybe 1 - 2 minutes between "ok" and the 35,6 With new sensor and latest firmware the afr stay at 35,6 every time but with setting "open loop" i can drive the car, it runs ok I have found no obvious exhaust leaks I have found afr gauges with the same bosch lsu 4.9 sensor, maybe i should buy one ? Than i would know if the Sniper EFI is wrong and if i go back to the Q-Jet, the afr gauge is still useful
Update: This afr gauge arrived today: https://www.summitracing.com/parts/avm-30-0300 The Bosch LSU sensor has the same part number as that of the Sniper efi First test, AEM gauge with old (second) sensor, it shows full lean Second test, AEM gauge with its own new sensor, shows correct values ( hoping the second sensor was bad ) Third test, using the Bosch LSU sensor from AEM gauge connected to the Sniper, afr ok for 10 seconds, then again go up to 35,6 Last test, AEM gauge again connected to the sensor still shows afr is good waiting for some small parts to bring the Q-Jet back to life ...
