I have a 2006 Ford Fusion 3.0L V6 that misses on cylinders 4, 5, and 6. It seems to happen going down a long downhill, though this may just be confirmation bias from seeing other people with that specific issue. I have replaced all 6 spark plugs.

I've attached a csv of some data I logged while driving. It seems like when it misses the O2 sensor and fuel trim for that bank both go to 0. Not sure if this is the O2 sensor losing connection or because it's going into open loop.

I drove that car a bit with the front O2 sensor disconnected and I believe the car was in open loop but I got the misfire again. I may have to try this again.

Should I just go ahead and replace the O2 sensor to rule that out?

 

 

Does your tool provide any oxygen sensor voltage readings ?

The readings would tell us if the sensor is functioning or complete loss of signal.

If the system goes into open loop, the other bank readings could be affected also.

If the sensors have been in there a really long time, they can be a bugger to remove.

 

Yes it does, the csv in my first post contains that info. When the car is misfiring, it seems like the O2 sensor and fuel trim on the same bank both go to 0.

Edit: here are the codes

https://imgur.com/a/KPu9xGp

 

DTCs from your outside link shown above.
Pinpoint-ALL.pdf attached previously.

 

Could you have a serious intake air leak on cyl1,2,3,side causing the PCM to be attempting to correct that by adding fuel and resulting the cyls 4.5 and 6 to be overly rich?

Any signs of an exhaust leak on the 4.5,6 bank ?

 

When I get on the gas the exhaust is awfully loud, but I haven't had any luck finding a leak. It sounds fine at idle but awfully loud at higher rpm

 

You need to repair that exhaust leak and the oxygen sensor information to the PCM will straighten out a lot of problems.
There is very likely nothing wrong with the oxygen sensor.

Check the area where the exhaust manifold bolts to the engine.

 

A little more info, it seems like right before it starts missing the bank time fuel trims climb high. And frequently bank 2 will be a similar value but different sign compared to bank 1; if bank 1 is +10% then a lot of times bank two will be around -10%.

Understood on the exhaust leak. What's the best way to test around the exhaust manifold? It's hard to see in there. Is it safe to assume that the bank that's missing is the bank that has the leak?

 

Extreme care is required when using the following method around a running engine.

A 2-3 foot piece of hose one end held close to your ear and moving the other end around the exhaust parts of the engine will help pin down the area of the loudest noise..