12mpg even after a much needed upper 60K

[zacritz929]

My SHO had alot of oil in the plug wells so I did an upper 60k. Before the 60k I got 12mpg and even after it I still get 12mpg.

I only have two codes:
172 (R,M) Oxygen sensor not switching - system is or was lean - Single, Right orr Rear HO2S - Fuel control

327 (O,R,M) EGR feedback signal is/was low - EVR or PFE

Ive read on how to test the o2 sensors and ill try to test the rear one. How bad will this hurt my mpg?


But for code 327.....Does this involve the EGR or DPFE? Will this affect my mpg?

 

[F-22 Raptor SHO]

The dpfe is part of the egr on the atx. If that is tripping a code, you can try cleaning it out. It is the square box that is bolted to the back plenum of your intake. Check the vac lines to and from it. Yes, that could impact your mileage.

12 mpg though is horrible, you need to consider other causes as well. Yes that o2 is probably bad, replace them both though, not just the one.

Check to make sure your e brake isnt sticking too.

 

[dantheman68]

this sounds like a brake issue... or a leaking gas tank...

12mpg is terrible

 

[NJSHO]

Ive read on how to test the o2 sensors and ill try to test the rear one. How bad will this hurt my mpg?

Ive also heard that the test that is up on shotimes will tell you if the sensor is good, but will most likely destroy it. If the sensors are old just replace both of them. Also, check to see if your butterflies are working properly. If they are stuck open you will get crappy gas mileage. Then make sure your thermostat is working properly (dont trust the gauge on the dash.) After that, you want to try replacing the sender that sends coolant temp info to the computer, it is different than the sender that operates the gauge on the dash. If either the thermostat is bad or the sender to the computer is bad, the computer thinks the engine is cold and dumps in extra fuel. I think you probably have a combo of problems.

Getting 12 mpg you should have raw fuel spitting out of your exhaust
I got 12mpg while on track running at full throttle/high rpm for most of the time.

 

[sho_sc]

Stuck injector?

 

[Hank F.]

My problems were cured by a new thermostat and vacuum hoses. I also replaced the O2's- which accomplished nothing, so maybe next time I will pay closer attention to my codes. Winter was also more of an mpg drain than I expected, too. Good luck.

 

[zacritz929]

Ok... thanks for all the ideas on what could cause my horrible mpg.

First my e brake cable is cut so I dont think my brakes are sticking at all.

I put a new cheap $6 AZ brand t stat in it. Im guessing I should get a Motorcraft?

My butterflies seem to be working fine cause the car hauls at 4,000 rpms.

I figured if the ECT was bad it would trip a code. Could it be faulty without sending a code?

First off Im going to get some carb or intake cleaner and clean the dpfe and egr up. Im short money right now so I cant get o2s but thatll be the next thing on the list.

 

[NJSHO]

My butterflies seem to be working fine cause the car hauls at 4,000 rpms.

Your car will still haul at 4,000 with the butterflies stuck open, because in normal operation, the butterflies open at 4,000. The problem with stuck open butterflies is that the secondaries are open in the sub 4000 rpm range. The quick way to check is to start the car and then rev the throttle @ the throttle body and watch the butterfly assembly, if at a hard rev something moves on the assembly then they are working correctly. If they aren’t working, check the electrical and vacuum connection on the back of the intake.

If the ECT is putting out some value it wont trip a code. Im not even sure there is a code for the ECT. It could be outputting a value the computer considers reasonable, but it could be stuck outputting a value corresponding to a low temprature.

Thermostat should have at least 1 jiggle valve and they need to be in the correct position.
See here:
http://www.shotimes.com/php-bin/mod...e=article&sid=262&mode=thread&order=0&thold=0

 

[93rev2sev]

NJSHO he probably feels them opening. Stuck open butterflies will not provide a kick in the pants at 4k, but a more gradual "improvement" as 4k is approached.

Ive run with a stuck open thermostat for 4 months. My MPG did not go below 20.

The rear flexible brake hoses collapse and cause the rear break to stick. It might have nothing to do with the e-brake cable.

It may sound elementary, but make sure you have good tire pressure and a good alignment. If you have decent tires, run 35 lbs or so.

Do a few coast-down tests to see how long it takes on fresh flat blacktop to coast in NEUTRAL from 70-40 MPH. Use the same streach of road several times and post your times here to see if anyone can tell you if it sounds right in an ATX(I have an MTX so the times will be off..slightly). This should tell you if something is dragging.

 

[zacritz929]

Ive already replaced one of the brake hoses before. I recently had the brakes bled at a brake shop and the front brake rotors get hot but the back stay cool. Im guessing the hoses are bad.

 

[rocket455]

you really shouldnt drive it that much either, if you have cats. the excess fuel will be pouring out your exhaust, rotting your cats and your o2 sensors