I've got a 97 with a 4.2 and a 5 speed. Was getting oil in the coolant and coolant return pipe rotted off the lower manifold, so I replaced the manifold with a brand new one and a new lower gasket. The problems I'm having were there before all that, just wanted to give a little history. I'm getting really bad mileage, odo doesn't work but I'm only getting about 3 days on a tank of gas, where I was getting almost a week about 6 months ago with the same driving.

Now for some technical data: Bank 2 LTFT stays a pretty consistent 8% higher than Bank 1 at cruising and idle. Hard accel pegs Bank 1 at .8% and Bank 2 at 3.2%. As soon as I let off at cruising speed Bank 2 jumps to around 17% and Bank 1 goes to around 5%. Bank 1 stays there, Bank 2 eventually drops to 12-13%. O2 voltages seem alright, however the downstream on Bank 2 always seems alot lower than the other 4

When the engine is cold it runs great, but once it warms up is when I start getting the rough idle. If I sit for 15 minutes or so with the truck idling (I do service out of it so I do that often for paperwork) then shut it off, it has a hard time staying running the next time I start it, feels like a fouled plug that cleans up with rpms

 

You may have leaky injectors. I'd also consider changing the plugs and plug wires, use only Motorcraft. Coil pack may also have some cracks. When you pull the plugs, do a compression test. No codes?

 

Plan on plugs and wires this week, I'll do a compression test when I do them. Unrelated code, P0143 or 44 I think, fuel tank pressure sensor circuit

 

Another problem, may be related. Had a melted vacuum line last week, one of the real tiny ones, that rendered my ac vent control useless, just dumped it to the defrost. Found the bad hose, repaired it, but it still dumps to defrost for about 10 seconds after startup

 

You need to cut the bad section out and splice it with rubber vacuum hose. You also need to check the rest of the HVAC vacuum system, there's an accumulator and a check valve back there somewhere. The inner fender well has to come out for full access.

P0143 and P0144 are O2 sensor codes.

 

You're right, just checked again it's P0443