Been having issues with my 97 mounty 5.0l V8.

First, it seems to idle rough. The rpm needle will fluctuate a few hundred RPM when hot and cold (audible increase and decrease in RPM), and it seems to shake intermittently when idling. I dug around and saw that my intake air filter is dirty (not awful, but definitely not clean) and the hose leading to my throttle body and inside my throttle body is filthy (there was a label saying not to clean the inside of the throttle body, is this safe to do?)

Secondly, it came with a CEL for a P0513 O2 Sensor Circuit Slow Response Bank 2 Sensor 1. One sensor is loose, but this is not the sensor that caused the code. I checked the resistance across the pins, and got something like 6 ohms on the Bank 2 sensor 1, however no CEL is currently on and my torque app is not showing that code (although it says the cat test cannot complete, same result my mechanic got when it had the p0153 code) Keep in mind i did have to disconnect a big wiring harness under the console when I removed it to install a custom console.

thoughts? I was thinking about changing the air filter and cleaning the throttle body (if that is safe) for the idle issue, and plugs/wires some time this summer.

should I replace the o2 sensor now or wait until I get a CEL with the p0153 code?

 

So in summary you no longer have any active diagnostic codes according to Torque, but you do have the rough idle? Has the rough idle been present for a long time or only since you disturbed the wiring harness under the console?

If your throttle body is filthy along with the intake air tube, the PCV system may not be functioning properly and allowing oil in to the intake. I don't recall though if the engine in your V8 Mountaineer has an actual PCV system or not. There are a few Ford V8s that don't use a PCV valve for crankcase ventilation. If it were my vehicle, I would not hesitate to use throttle body cleaner to clean the throttle body and intake air tube, and have done so numerous times with no obvious ill effects. You might also want to pick up some MAF sensor cleaner and clean the MAF sensor as well. When is the last time the truck had a tune up, including at least spark plugs, spark plug wires, and the fuel filter?

Double check the code you read. P0513 relates to the Immobilizer system. P0153 relates to the O2 sensor circuit. Based on the definition and your last sentence, I think the first instance of the code number was a typo.

Also, let's make sure we're looking at the correct orientation. Bank 2 would be the bank on the driver's side of the engine, assuming you're in North America. Sensor 1 would be the sensor between the head and the catalytic converter.

-Rod

 

I did not notice the rough idle after removing the harness. and I meant p0153, not P0513, yes it was a typo.

Tune up? not sure...been working on that (bought it used 6 months ago, 169k miles). spark plugs are quite stuck in there, so i bet it has been a while...but the wires look ok. Any tips for removing a tough plug?

as far as the o2 sensor, ill probably wait until i get a CEL.

and yes, I do have a PCV on this engine

 

I don't have much to offer regarding getting the stuck plugs out. You could try spraying them with some penetrating oil before removing them. If you are not able to get them out that way and need to drive it, I'd recommend spraying off the penetrant with brake cleaner to cut down on the smell of burning penetrant.

Make sure you have a quality socket that fits the spark plug snugly and use a pivoting head long ratchet wrench to get on the socket straight and provide good leverage. You also will find several of the plugs easier to get to if you jack the front of the truck up, support it on jack stands, remove the front wheels, and go after the plugs from above the upper control arms.

-Rod