Did you say in the past that the forward O2 sensors affect MPG? I have no codes but have 130000 miles on them. Thought I would replace to help. Any thoughts?

 

yes they will have some effect on how much fuel ur burning. 130k is plenty of miles, replace them. how bad is your mileage?

 

The HO2S sensors are at the heart of the Fuel and Catalyst monitors.

The operation of the Emissions control in OBD depends on the sensors being at proper operating temperature. Both the catalysts and the HO2S sensors need to be at several hundred degrees before they are working efficiently, so we have heaters built in to the sensors on these trucks that bring them up to operating temperature as soon as possible. Because the HO2S sensors need to operate at near stoichometry they cannot be used when rich fuel/air mixtures are needed and so..... - For 180 seconds from cold start the system is Open Loop - fueling is arranged as a function of temperature, (ECT(if u has 1), IAT) and air input (MAF) etc, with no reference to stoichometric (lamda) levels.

- Well,the engine is in open loop during WOT (Wide Open Throttle).
When the engine is in negative torque (ie overrun, engine being driven by transmission) fuel may not be delivered via the INJectors at all. During such periods fueling is in Open Loop.

The HO2S sensors are numbered so that the upstream sensor 1 is always on the Bank which contains Cylinder # One. The down stream sensor is numbered 2.

Yes - Economy,efficiency are effected. Your still within parameters if your not getting a MIL (CEL), it's really up to your discretion - Hows your warm idle? Your computer will let you know when there's a problem. - It's still a good idea to change them @ 100k plus miles. Only use OEM Bosch sensors or don't bother. There's cheaper sensors out there , but they'll cost you in the long run.

Your O2's are just a part of what makes for good economy. Plugs and various other sensors need to be in good health as well.

 

You are correct. The ECM varies the fuel injector pulse width based on the output voltage of the forward O2 sensors. If the O2 sensors are lightly fouled they cannot properly sense the O2 in the exhaust and as a result the ECM may dump in more fuel that is unneeded and lowering fuel mileage.

 

The milage is strange I have been getting 17 city and highway. But do I need to do all four or can I cheat with 2? I am a firm beleiver in OEM. OEM got my last 4 Fords over 250000 with no major issues.

 

rears only monitor catalyst efficiency. No need to change them unless you have had cat failure and burned the sensor up

 

Cool Thank You I thought I seen that in a post here but I could not find it. There is way to many post to search and the search kind of bits.