I want to replace the 4 o2 sensors on my 98 F150 5.4 L. They are all 4 wire but how do I know which ones to buy? There are a bunch out there on the web that are cheaper than the local auto parts store. Any suggestions?

 

Hi BCC1313 and welcome to FTE

I would buy genuine Ford ones. The aftermarket ones I've seen weren't very good...had to swap connectors etc.
I also wouldnt replace the back sensors unless there is a definate problem with them. They arent really used as O2 sensors. They are used to monitor the catalytic convertors to make sure they are working properly. Ford's prices on parts arent always more than the aftermarket and if you only buy 2 instead of 4 you might actually get away cheaper than you were thinking.

 

Thanks for your help. I have another question...what's the proper spark plug gap for the same 98' F150 V8 5.4L ?

 

0.052-0.056"