'98 explorer 5.0L P0133

Hey folks, I have a 98 explorer 5L that is logging a P0133 code. (bank 1 sensor 1 slow circuit response) I replaced the 02 sensor, but still logging this code. I do have a small exhaust leak that I cannot find, as I can only hear it under load....sounds like a collapsed lifter which makes me think its a header leak. Would a slight exhaust leak cause this fault code? If so, any ideas on how to pin point where the leak is....the is ohhh so much room under the hood check around the headers and stuff. Any input would be great. Thanks guys

From the factory service manual, the possible causes for this code are:
Possible causes:

-- Contaminated HO2S.

-- Exhaust leaks.

-- Shorted/open wires.

-- Improper fueling.

-- MAF sensor.

-- Deteriorating HO2S.

-- Air leaks.

So your exhaust leak could certainly be contributing to the code. As for finding the source, if you aren't able to do a thorough visual inspection, looking for traces of black carbon, you might need to take it to an exhaust shop and have them inspect it. Keep in mind though that if you get the front end off the ground, remove the front wheels, then look through the wheel wells you might be able to inspect a lot more than you can from the hood. This is also the trick for replacing the spark plugs. It actually makes changing the plugs on the V8 not bad at all.

-Rod

Look closely at the exhaust studs. They are bad about breaking over time and causing the noise you describe.

Thanks for the reply guys....will check into that stuff you mentioned tomorrow after work. Now a friend of mine had a 95 F150 5L and the pipes off the air pump that go into the back of the cylinder heads rotted out and started to leak and created a similar noise under load. My explorer does not have an air pump (that I can see) but would the heads have the ports in the back for the air pump piping that would just be blocked off and maybe one of the "plugs" is leaking? I cannot see that back of the heads no matter how I look. Thanks again!!

Thanks guys. I was also wondering if the heads on this explorer would be the same as the heads off a 95 F150 5L, with regard to the F150 having an air pump pumping air into the heads?