Bad MPG on 98 EB V8 AWD

[idoticsoigpa]

I have had this Ex for a year now. MPG used to be better, but has gotten worse. On a road trip it will get 15 to 17 MPG. I used to have another EX identical to this one and it got 18-19 MPG on the highway. I just filled up and got 12 MPG. All the basics have been covered, plugs, wires, filters, etc. I throw a code P0133 (slow response time on bank 1, sensor 1) about every 2 to 4 months, I kill it and it comes back. I read that this might cause low MPG. Also, the bad MPG started about the time the Ford dealer flashed the PCM. Could this be it? The Ex otherwise runs great. Does anyone have real world experience with O2 sensors and/or reprogrammed PCMs causing bad MPG?

 

[FIND]

Whenever they throw O2 sensor codes, they richen the mixture to try and control NOx emissions and exhaust temperatures. 17mpg is what these SHOULD get on the highway, but there is no reason for them not to get better. I wouldn't blame Ford re-flashing your PCM, more than likely, it was either a coincidence, or you just noticed it because you just had work done. If you are consistently getting that same code, I would assume your O2 sensor is bad. They aren't expensive to order on rock auto, just replace your bank 1 downstream O2 sensor. It isn't a really tough job, but they are hard to get out after they have been in there for a number of years.

 

[idoticsoigpa]

Bank one O2 sensor one doesn't want to budge. Just going to let Ford dealer do it. Sometimes I just don't want to deal with stuff like this, and this is one of those times.

 

[71cutty455]

Before taking it to the dealer try running the engine for a couple minutes to let the exhaust pipe warm up. That will expand it a bit and the sensor should come out much easier.

 

[FIND]

Before taking it to the dealer try running the engine for a couple minutes to let the exhaust pipe warm up. That will expand it a bit and the sensor should come out much easier.

This^^^ That, and get a good sized cheater bar to start your stuff turning.

 

[dcdyd]

I would take any oppotunity to deal with my 98EB V8 if I can. It is harder to replace B1S1 than B2S1. But it is not impossible for DIYer. I just did it coupler month ago after driving the truck for about 14 years. This thread should give you all information.

 

[white_shadow]

Before taking it to the dealer try running the engine for a couple minutes to let the exhaust pipe warm up. That will expand it a bit and the sensor should come out much easier.

the sensor will heat up also, i would not do this. pb blaster it the day before, then try it. if that does not work heat just the bung with a torch, then it will come out.

 

[dcdyd]

Before taking it to the dealer try running the engine for a couple minutes to let the exhaust pipe warm up. That will expand it a bit and the sensor should come out much easier.

I ran the truck for couple minutes before trying to get it off. I believe that it helped.

 

[FIND]

the sensor will heat up also, i would not do this. pb blaster it the day before, then try it. if that does not work heat just the bung with a torch, then it will come out.

The sensor expands at a different rate than the bung. That is why they get stuck in the first place.

 

[DieselHilux]

Downstream oxygen sensors only monitor the cats efficiency and do not control the amount of fuel going into the engine.

 

[FIND]

Downstream oxygen sensors only monitor the cats efficiency and do not control the amount of fuel going into the engine.

The ECU adjusts fuel and timing to control emissions.

 

[CDW6212R]

That sounds like one of the emissions sensors or devices, or the O2's. Those codes usually don't actually mean the O2 sensor is bad, the sensor feedback is telling the PCM that something else is wrong. Now that these all have high mileage though, the O2 sensors are going to be bad more often etc.

I'd find out what the past records show for maintenance of the O2's and maintenance items. If anything is known to be relatively new, I would not worry about that part. Clean the IAC really well, and the EGR gently, avoiding the rubber diaphragm with any cleaner.

If nothing amongst those and what you have done helps(try Seafoam too if you'd like), then start replacing the other emissions items. I'd put the DPFE sensor high on the list, it doesn't generally throw those kinds of codes, but it does affect emissions and they are know to go bad after many years, old age. Do the front O2 sensors if the mileage is over 150k.

Buy parts online if you can, that is much cheaper.

 

[DieselHilux]

It uses the upstream sensors to make adjustments to the air fuel ratio. The downstream sensors purely monitor the cats.

And if the sensor is slow to respond that is only caused by a dieing sensor.

 

[FIND]

It uses the upstream sensors to make adjustments to the air fuel ratio. The downstream sensors purely monitor the cats.

And if the sensor is slow to respond that is only caused by a dieing sensor.

Yes, I know this. What I am trying to say is that the ECU makes changes to the mixture and timing when it thinks the catalytic converters are not operating efficiently to control emissions. No, it doesn't use the downstream sensors to calibrate the fuel mixture, but when they are not functioning correctly, it does change the mixture to control emissions. That is why I said the mixture is changed from throwing an O2 sensor code.

 

[DieselHilux]

Yes however it will not affect mileage that much, honestly if you want really good mileage you need a good custom tune and a clean airfilter and free flowing exhaust.

A custom tune that deletes the emission programming and has a more aggressive spark advance map will make a huge difference!

 

[white_shadow]

Yes however it will not affect mileage that much, honestly if you want really good mileage you need a good custom tune and a clean airfilter and free flowing exhaust.

A custom tune that deletes the emission programming and has a more aggressive spark advance map will make a huge difference!

if you want fuel mileage, you are in the wrong vehicle

 

[FIND]

Yes however it will not affect mileage that much, honestly if you want really good mileage you need a good custom tune and a clean airfilter and free flowing exhaust.

A custom tune that deletes the emission programming and has a more aggressive spark advance map will make a huge difference!

While I would generally agree... Surprisingly enough, I broke the wires to one of my downstream O2 sensors and subsequently only got 16mpg on a highway drive when I would normally get 20. Also, eliminating emissions programming isn't necessary to get better mileage, and while it works for someone who lives in a state without emissions testing, it is still technically illegal.

 

[idoticsoigpa]

Bank 1 sensor 1 replaced, MPG improved 2 MPG. Got 14.7 mostly city driving. Not bad, and just where I think it should be. Runs smoother too.

 

[FIND]

Thanks for posting your results!

 

[SoNic67]

Before taking it to the dealer try running the engine for a couple minutes to let the exhaust pipe warm up. That will expand it a bit and the sensor should come out much easier.

Pipe will EXPAND in all directions therfore the O2 hole will SHIRNK.