I am new to the forum (and very inexperienced with cars) but came for help so I will get right to it. 2004 F150 Heritage XLT, V6 4.2L, 2WD 4-SPD. First, I have been getting a rattle which seems like passenger side when the truck is first started around 1000 RPM which lasts a few seconds and is fine when settles into idle. Rattle also occurs when accelerating right at 1000 RPM but again only for a second. It has not gotten worse and becomes less noticeable once car has been driving and warmed up. Thought it might be something loose like a heat shield but dealer couldn't find anything and said it could be the catalytic converter breaking up but not to worry about it.

Next, about 2 months ago I started to get a high pitched wine around the passenger side when I first started the car right around 2000 RPM but again lasted maybe 10-15 seconds and was fine when it dropped down below 2000 and into idle. This didn't happen every time I started the car but was more noticeable when it was really cold out. It then started occurring while driving when the RPMs were at 2000. But again not all the time and went away once the car was warmed up. The rattle still occurs as well.

Then about a month ago the service engine soon light came on and I took it to the local Ford dealer. They pulled a p0174 code (bank 2 system lean) and replaced o2 sensor 1 on bank 2. They also noticed that bank 1 CAT is rattling internally but still working. The rattle and whine still continued to occur and the service engine light has returned. I went to Autozone and they got the same p0174 code with a possible bank 2, sensor 1 problem. So if it is not the o2 sensor what could be the problem? I don't want to repeatedly spend money at the dealer when they can't find the real problem. The truck seems to run fine but takes a while to warm up in the cold. Sorry for the long post but any help is greatly appreciated.

 

Find a different shop - you don't change the O2 sensor for a lean code. You probably have a vacuum leak or unmetered air entering the intake after the MAF sensor, or possibly an exhaust leak on the driver's side upstream from the O2. It *might* need plenum gaskets and isolator bolts. The rattle probably is the cat coming apart internally. The whine may be one of the driven pulleys - idler, tensioner, alternator, power steering, etc. A weak battery can cause an alternator whine. Slow warmup can be a faulty thermostat or a fan clutch that's not disengaging.

 

Thanks for the advice. If the shop didn't fix the problem the first time and the same code comes up again are they obligated to fix the problem without charging me an arm and a leg for additional repairs?

Also a correction to my first post: the whine occurs at 1500 rpm, not 2000.

 

I agree with glc, you don't need to change the o2 for reporting an issue. You have a lean condition detected, vac leak is most common.

Check the hose that goes to the PCV on the side of the throttle body, that is usually the first to go. If it is soft and squishy then replace it.

The rattle could also be a bad PCV valve.

What you are calling a whine may be a vac leak making a sucking sound. Look around the battery area to see if all the vac lines are solid.

Also go back to the dealer and demand the money back for the o2 sensor, they should know better. That is an Auto Zone type of diagnosis, shame on them.