V12 Bank A running rich, Bank B normal
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From: Calgary, Canada
V12 Bank A running rich, Bank B normal
The car: 1994 6.0 V12, with air injection and cats. 185,000 km.
Over the winter I did a lot of work to the car, I had the intake manifolds off and replaced the gaskets, new valley plate gasket, new distributor cap, rotor and spark plugs, new ignition modules, new oil cooler and lines, new water pump, new air injection check valves, and new O2 sensors. This started by needing to fix large oil leaks and spread in scope, as these things do.
Now when I start the car, the right (A) bank is running rich. I have a wideband AFR meter and putting it in the tailpipe ( so post catalytic converter) after the air pump shuts off I am getting AFR on the right of about 13.1, and on the left 14.2 ( as I would expect). I checked the manifold vacuum level and at idle I am getting 17" Hg, which is very healthy for my altitude. The exhaust feels smooth and even, and the car idles smoothly, so I don't believe it is an ignition problem. The exhaust smells rich on the right side.
After I got the car back together I did a short test drive and an ignition module failed, so I know what a single bank Marelli failure is, and the car is now running on all cylinders.
Looking over the wiring diagram, about the only thing that seems related to a single bank is the power resistor box. I did take that out tonight and measured the resistance across the center pins and it is 5.9 ohms on both sides, as it should be. I cleaned the connections on the power resistor box plug ( which did look like they had some corrosion). I did notice that the socket in the box was loose, is this normal? After cleaning, there was no difference in the AFR, still rich on the right bank.
I also had a check engine light come on and FF44 indicated, which is the O2 sensor not registering a change after the ECU biases the mixture rich or lean, on the right bank. So the ECU is telling me I have a problem on the right bank. The manual says that it clamps the adjustment at the midpoint when this code is set.
As far as I know I don't have a vacuum leak, as the engine has nice strong vacuum. Almost everything else I can think of would affect all cylinders, not one bank.
Any ideas where I should look next?
Over the winter I did a lot of work to the car, I had the intake manifolds off and replaced the gaskets, new valley plate gasket, new distributor cap, rotor and spark plugs, new ignition modules, new oil cooler and lines, new water pump, new air injection check valves, and new O2 sensors. This started by needing to fix large oil leaks and spread in scope, as these things do.
Now when I start the car, the right (A) bank is running rich. I have a wideband AFR meter and putting it in the tailpipe ( so post catalytic converter) after the air pump shuts off I am getting AFR on the right of about 13.1, and on the left 14.2 ( as I would expect). I checked the manifold vacuum level and at idle I am getting 17" Hg, which is very healthy for my altitude. The exhaust feels smooth and even, and the car idles smoothly, so I don't believe it is an ignition problem. The exhaust smells rich on the right side.
After I got the car back together I did a short test drive and an ignition module failed, so I know what a single bank Marelli failure is, and the car is now running on all cylinders.
Looking over the wiring diagram, about the only thing that seems related to a single bank is the power resistor box. I did take that out tonight and measured the resistance across the center pins and it is 5.9 ohms on both sides, as it should be. I cleaned the connections on the power resistor box plug ( which did look like they had some corrosion). I did notice that the socket in the box was loose, is this normal? After cleaning, there was no difference in the AFR, still rich on the right bank.
I also had a check engine light come on and FF44 indicated, which is the O2 sensor not registering a change after the ECU biases the mixture rich or lean, on the right bank. So the ECU is telling me I have a problem on the right bank. The manual says that it clamps the adjustment at the midpoint when this code is set.
As far as I know I don't have a vacuum leak, as the engine has nice strong vacuum. Almost everything else I can think of would affect all cylinders, not one bank.
Any ideas where I should look next?
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