I'm in the process of replacing the intake/exhaust manifold gasket on my 4.0L and was greeted by some really heavy carbon deposits inside the intake manifold, extending into the cylinder head. This stuff is wet and gunky, and I'm sure it's not doing anything good for my engine. I ran a can of Seafoam engine cleaner through the intake only 75 miles ago, so I'm surprised to see this much build-up.
What do you think caused this to happen? My immediate thought was piston rings, but the air filter is clean and the motor really doesn't use any more oil than usual (for a Jeep). Oil pressure, per the dash gauge, does seem low -- it stays at 40 psi while driving and dips down to 15 psi while idling, but I understand that's a common thing for these engines. Might even be the sending unit, who knows.
Now, I've been averaging about 12 mpg... way less than what it should be. I've been suspecting an intermittent oxygen sensor was causing the engine to run richer than necessary, which could account for the carbon I'm seeing. Would a rich condition cause this much gook?
What do you think caused this to happen? My immediate thought was piston rings, but the air filter is clean and the motor really doesn't use any more oil than usual (for a Jeep). Oil pressure, per the dash gauge, does seem low -- it stays at 40 psi while driving and dips down to 15 psi while idling, but I understand that's a common thing for these engines. Might even be the sending unit, who knows.
Now, I've been averaging about 12 mpg... way less than what it should be. I've been suspecting an intermittent oxygen sensor was causing the engine to run richer than necessary, which could account for the carbon I'm seeing. Would a rich condition cause this much gook?