stufarmer

I own an 04' GT Convert/Auto. My fuel economy has dropped off slightly over time down to the 14-16 mpg average. Recently I completed a Major 60,000 service. All Motorcraft tune-up parts, plugs/filters/T-stat/coolant, Seafoam Top end and T/Body cleaning along with hoses/belt, A-Trans & R-Diff services. I've seen a slight increase to about 16 mpg average. Have any of you changed all the 02's or EGR & Sensor or MAF and seen a MPG gain. The car has never had a CEL on.

CalBoy101

If it still has the original 02 sensors in it its time to change them out. www.rockauto.com has good prices on the Denso ones which are the same as the originals.

You really only have to do the front ones as the rear ones don't affect the engine operation, they only monitor cat condition. The fronts are a pain to swap though, its easiest to drop the front pipe down so you can get to them.

You can just clean the MAF sensor, get some MAF spray, pop the MAF off and give it a good spray clean, the tiny little element in the center is what needs to get cleaned.

Clean the EGR and PVC valve with some carb cleaner.

petrock

O2’s don’t really wear out. They either work or they don’t. They are not a regular maintenance item that needs to be replaced periodically. Most common failure is the heater circuit fault. If something is wrong with them a code will typically be thrown.


That is (partially) incorrect. I’ve covered this in many posts on this forum, but it doesn’t appear to be sticking. The rear O2s do monitor the efficiency of the cats, but they are also taken into account by the computer to determine fuel trim numbers.


+1. Cleaning the MAF is a good idea. A dirty MAF can cause all kinds of problems. Especially since you have a K&N oiled filter, some of that oil may have gotten on the MAF (a common problem) and is messing up its readings.


While I don’t think it will have much of an effect on the MPG, these are also good ideas.

stufarmer

I would have sworn the 02's were maintenance items, that's why I asked. By doing the suggested services and cleaning do you believe I'll see a fuel economy increase.?

Stevo86

O2 sensors can certainly wear out, the zirconium coating on the outside can get coated with soot or it can wear off due to the intense heat. The heating element inside can also degrade causing poor ionization of the O2 molecules which leads to no electrical transfer.

A poorly functioning but not broke O2 will still work, but it will work slowly. That leads to inefficiency.

Also no the rear oxygen sensors have ZERO to do with fuel trim. If that were in the strategy the engine would think it always needed fuel, a properly functioning car has a flat line on the rear O2 waveform. They always read lean in a car with cats.

cliffyk

This is not so. As narrowband sensors age there output voltage falls, and it can fall by as much as 15 to 20% before the PCM interprets this as a failed sensor. However during this period while the output voltage is too low, yet sufficient, the PCM will believe the mix is lean and add fuel making it actually rich consuming more fuel than needed.

More about narrowband O2 sensors.

Negative. The rear (Ford refers to them as the Stream 2 sensors) O2 sensors do nothing but monitor the cats. This can be verified in the Shop Manual's functional descriptions of both the Catalyst Efficiency Monitor and Fuel Trim routines.

This is also evident in the Catalyst Efficiency Monitor section of Ford's OBD System Operation Summary. The OBD summaries for the various model years can be downloaded from the Motorcraft Service Publications website.

There were some 2003 Ford models that met the Partial Zero Emission Vehicles (PZEV) standard. They used 3 sets of O2 sensors in which front (Stream 1) sensors provided the primary fuel control monitoring, the center (Stream 2) sensors monitored the cats. The rear set (Stream 3) were used to calculate a very long tern fuel value used to maximise cat efficiency. No New-Edge Mustangs used the PZEV system.

CalBoy101

I can't agree with that one, the repeated heat cycles and moisture gets to them, on a car I care about I swap them at 20k, on a normal car 50k.