Fuel fouling one side only

[cliffdippel]

Jeep liberty, 77000 miles, engine light on, fuel lean code, downstream o2 sensors replaced, Assume some kink of vaccumn leak? Passenger side spark plugs are carbon fouled, drivers side clean. Extremely poor fuel consumption.

What would be most likely to cause one bank of plugs to all foul from fuel rich mixture and not the other side.

[fredjacksonsan]

This is the 3.7 liter V6 if I'm not mistaken?

For me this would point to either a fuel delivery problem (if there are separate sides to the fuel line) or an ignition problem.

I would check the coil/ignition for the over rich side first.

[cliffdippel]

Thank you for the quick reply. The Liberty V6 has separate coils for each cylinder. I could swap sides for all of the coils to test but it would seem strange for all three coils to go bad on one side.

[fredjacksonsan]

You may want to check the voltage going to the coils on each side, and compare them to make sure they are the same.

How long has it been since you replaced plugs?

Also, correct me if I'm wrong but is this distributorless, with no plug wires?

[cliffdippel]

That is correct, six cylinders, six coils, new premium plugs. What is the best procedure to check the incoming voltage. I would guess that I would have to disable the fuel system and run the fuel rails dry to protect the catalytic converter from being doused with fuel?

[fredjacksonsan]

I had a 2004 Dodge Truck with the same engine. IIRC there is a module that directs the voltage to signal the coils to fire - and it is split into two sides. I'd locate and check the voltage coming from the module.

Hopefully someone a bit more knowledgeable will be by shortly.