O2 Sensor help...
Thread Starter
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Postmaster
Joined: May 2002
Posts: 3,028
Likes: 1
From: Annapolis, Maryland
O2 Sensor help...
I've never checked or replaced my O2 sensors before, and I'm at 71K miles. I'm going to go ahead and change them, but I can't even figure out how many I've got or which ones I should replace. They haven't set off the idiot light, but my gas mileage has gradually gotten worse, so I'm thinking I should go ahead and replace them. From what I've read, I've got 3 sensors - 1 in each exhaust manifold (I've seen the driver side one with my own eyes) and one behind the cat which apparently just monitors the cat's effectiveness. Are all my sensors accounted for? Should I replace all three, or just the two upstream sensors and leave the downstream alone?
Thanks for your help!
XXL
Thanks for your help!
XXL
Senior User
Joined: Feb 2003
Posts: 369
Likes: 0
From: Bronx, New York
O2 Sensor help...
Hey Matt, I just went through the same thing. I think you have 4 sensors, 1 on each manifold right after it bolts to the downpipe, and 1 for each cat. Unless the layout was changed for 99, you should have the same layout. The downstream ones or "cat monitors" as the dealer likes to call them, are a snap to change. The upstream ones are a pain because they thread in from the engine side, and give you little clearance to back them out. The Ford repair CD shows a special service tool being used for this procedure, as well as just over a 1/2 hour repair time, for each. As far as swapping them all out, if they are not throwing out codes, I would do the upstream ones first. They list for $90 apiece from Ford, probably less aftermarket, so it would be a little expensive to do the whole lot at once. Do the upsream ones first, and see what kind of results you get, Remeber to clear the ECM............Rich
Thread Starter
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Postmaster
Joined: May 2002
Posts: 3,028
Likes: 1
From: Annapolis, Maryland
O2 Sensor help...
1 step ahead of ya, Rich -I finished them yesterday. I jacked up the truck, took off the front wheels, and pulled back the plastic fender well covering. The driverside one wasn't too tough, but the passenger side gave me the fight of a lifetime! After fighting for 3 hours, I ended up taking out the tranny dipstick tube, and I was done 20 minutes later. I replaced the fuel filter today, as well. I'm preparing for my 70 mile-a-day commute back to school in the fall. Next on the list before September are the plugs.XXL
