Rich Misfire Issues at Cruise

[1984rampage]

Having an issue at cruise in vacuum where the AFR's will oscilate between 10.0:1 to 14.8:1. Vehicle will misfire/stumble and go completely rich on the wideband. It only does this in vacuum and runs great as soon as it hits anything above 0PSI. Its really annoying driving long distances having to constantly play with the throttle to keep the vehicle from going full rich and misfiring.

I have tried leaning out the part throttle fuel tables and also the base fueling from 22" of vacuum all the way to about 2 PSI, but that didnt do much.

Vehicle is an 87GLHS, 87T2 electronics, running the 2.5L_MTX_Custom_v13 turbonator cal.

There are no codes being thrown.

Could this be a timing issue?

Any ideas on where to start looking?

[1984rampage]

Anyone?

[mpgmike]

How old is your oxygen sensor? When the O2 sends low voltage, the ECU sees a lean mixture. If your O2 sensor is tired, it will send lots of low voltages. The ECU will then richen the mix to get the volts back up. If your WB is an Innovate, it has a simulated NB output you could send to the ECU. Save you the price of a new NB.

Mike

[turbovanman²]

Is that one of Rob's new templates or older ones? He's fixed alot of issues in the new versions.

[shadow88]

From my understanding, rich misfires occur at around 8:1 give or take a point or 2

However, an ignition fault can show rich on an oxygen sensor as there is unburnt fuel and air (oxygen) being passed straight through the engine. I would look into ignition related problems first. Plugs, gap, wires, coil, base timing, cap and rotor condition, correct wire engagement into the cap, ect.

[mpgmike]

Just a minor correction, misfires register as LEAN, as the sensor ONLY SEES THE OXYGEN, not the fuel. If the oxygen isn't consumed in combustion, it gets exposed to the sensor.

Mike

[1984rampage]

Just a minor correction, misfires register as LEAN, as the sensor ONLY SEES THE OXYGEN, not the fuel. If the oxygen isn't consumed in combustion, it gets exposed to the sensor.

Mike

Thats what I assumed. When the wideband drops down to 9.8-10:1 is when the car will stumble/miss. My wideband is an innovate, so I'll definitely try sending the simulated signal in order to rule out the oxygen sensor.

[shadow88]

Just a minor correction, misfires register as LEAN, as the sensor ONLY SEES THE OXYGEN, not the fuel. If the oxygen isn't consumed in combustion, it gets exposed to the sensor.

Mike

Dammit, I know that too! Glad you caught that.

[1984rampage]

Ran the simulated narrowband signal to the ecu.. Vehicle is still doing the same thing, so it wasn't the stock O2... Any other suggestions