Downstream O2's and rough running

[Dirky]

Hey guys,

Just finished installing the transmission on my 2000 F-150, 4x4, 5.4L a little while ago. I removed the tranny to do the input shaft seal, and did the rear main and transfer case seals while I was there. 4R70W

I've got an issue though...

I am experiencing a rough running and misfire when driving the truck. My down stream O2 sensors are not reading on both banks.

I've checked my connections, but I'm not sure where else to look. With both sensors being out, I'm thinking there is a common problem between the two, possibly the ground.

What do you think?

Thanks.

 

[blacksnapon]

What do you mean "not reading"? Are they not changing (which would be normal). A misfire wouldn't be caused by downstream sensors. They're also known as catalyst monitors (essentially just showing if the cats are working).

 

[Dirky]

They are not switching, they read .000 volts on the scan tool. I should have something happening, if they are both dead, something must be wrong.

 

[blacksnapon]

They are not switching, they read .000 volts on the scan tool. I should have something happening, if they are both dead, something must be wrong.

If they were not working, they will show the same data as the upstream sensors. They commonly wont show anything until the vehicle has been driven for some time.

 

[Dirky]

After further diagnoses, I found that the downstream sensors are in fact operational, and that my misfire was cylinder #4.

Pulled the COP and found corrosion from moisture. I guess by having a week to sit while I did the transmission, corrosion started.

I went ahead and cleaned out all the COP's and plugs, applied dielectric grease, and everything is great..

Thanks.

 

[blacksnapon]

After further diagnoses, I found that the downstream sensors are in fact operational, and that my misfire was cylinder #4.

Pulled the COP and found corrosion from moisture. I guess by having a week to sit while I did the transmission, corrosion started.

I went ahead and cleaned out all the COP's and plugs, applied dielectric grease, and everything is great..

Thanks.

#4 is commonly a problem because the heater hose just above it is leaking, causing the coil to short out.