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Discussion Starter #1
I am getting really bad gas mileage right now and I'm not sure why. I have a 92 Daytona R/T. I should be getting around 22mpg city but I'm getting 15mpg right now. Here is a list of everything I've installed on the car thus far that could have had an effect on my mileage:

255 Walbro Fuel Pump
Fuel Tank
Fuel Sending Unit
Everything in and outside the tank
SS Braided Lines under hood
Stock hard lines from the tank to the braided lines
Fuel Pressure Reg.
TIII Fuel Rail from TU
+40% Injectors
10mm Magnecores
Autolite 63's gapped at .032
New OEM Ignition Coilpack
FWD Stage 1 ECU (15psi)

I recently installed a Wideband kit and I monitor my ratio which is never rich except at WOT. I know everyone might be thinking "your fuel pressure is too high, your fuel setup is too rich, your injectors are too big, you have a fuel leak, you have a lead foot, blah blah blah." I hate to say that couldn't be more far from the truth though. My mileage was just as deplorable before I started all those mods and I do not constantly floor my gas pedal. I've been driving pretty conservatively. And like I said before, my A/F ratio tells me I'm not rich, but my mileage says otherwise. Any advice or troubleshooting options would be great. Thanks all.

-Eric
 

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You are the second person in a week complaining of poor fuel mileage.
The other was in GA.
Could be the fuel blend.
Are you guys back to normal since Ike?
 

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any codes ?

I would suspect the O2 sensor ...

are you running a simulated output from the WB (for the computer) or running stock O2 ?

can you put an old school narrowband AF gauige on yur O2 sensor to monitor ?


ethanol in gas causes poor mileage.
I have seen a report on the web that claims either no change or in some cases a slight FE increase with blends up to 50% ; doesnt make sense but ...
 

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So what is your afr at cruise ? I dont see any mention of an exhaust system wich is very important and +1 on the o2 sensor, they're supposed to be replaced every 60k miles
 

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Discussion Starter #7
I'm really sorry. I totally missed the fact that I didn't mention I replaced the O2 sensor also. I replaced it with the MOPAR 4-Wire, not the crappy Bosch one. The Wideband is for monitoring and tuning purposes only, it's not connected through anything else. I know Ethanol causes a slight decrease in mileage but that alone can't possibly be giving me the mileage of a V8. My area was uneffected by Ike. As for the Knock Sensor, idk, I assume it's working because I don't hear any knock, which would mean detonation caused from running lean (however, I'm not running lean, hence the poor mileage). My ratio at cruise is what it should be, 1 lambda/14.6 AFR (give or take). It seems like stop and go fluctuates the fuel gauge and sucks down most of the fuel. At cruise it's fine though. It's kind of hard to read the Wideband while accelerating through the gears though. It fluctuates quite a bit while doing so. Is it possible this is a Vacuum issue or a MAP Sensor problem? Maybe both?...That is the next thing on the list, I am redoing everything with a Vacuum Distribution Block. Any troubleshooting I can try in the meantime?
 

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Is your catylitic convertor clogged or a collapsed passage in the muffler ? do you have a scanner to check for malfunctioning sensors ?
 

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Discussion Starter #11
Stay out of boost :thumb:. A lot of the time my shadow gets worse mileage then my old caprice wagon with a tired 307.
No, sadly that is not the case here. I drive pretty conservatively because it's running like crap. Not to mention, with my FWD Stage 1 ECU, I should be getting 15 psi, but am only getting 6. I am also running lean now and the car stumbles and hesitates. The only time it seemingly runs ok is a cold start in cold weather or at WOT. The symptoms get worse by the day. I don't know..
 

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This is the 1st mention of driveabilty concerns.
All we were aware of was a fuel economy concern not a .....
"running like crap" or "the symptoms get worse everyday".
 

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Discussion Starter #13
That is because it wasn't an issue until halfway through the thread when I mentioned it. I turned up the fuel pressure last night and it seems to be helping. I am also redoing the IC and piping and I think it is going to help alot. I will post again when it's all done.
 

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Discussion Starter #15
I checked over everything once again and finally found the problem. My O2 code was being thrown because one of the wires on the harness had eaten through somehow. I just soldered it back, problem solved. I just filled up my tank yesterday, but the fuel gauge is not fluctuating anymore. That could be what will finally give me my good gas mileage. I'll post again when I have a good idea on where my mileage is. Thanks again everyone.
 

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Discussion Starter #17
Change your oil. There might be some gas in the oil. Oil is much cheaper than bearings and a crank grind.

Justin
I did change my oil recently but that didn't do a thing for gas mileage. All my other problems are fixed. I have boost back, the O2 harness has been re-soldered fixing the hiccups and lean issues.

BUT...my gas mileage is still atrocious. I don't think I will even make 200 miles on the current tank as of right now. I got 215 miles out of my last tank. That is about 16MPG. It looks like I'm getting about 14MPG on the current tank. What the heck is going on?? I still can't figure it out. It just doesn't make any sense. Everything is working how it is supposed to. I've replaced so many flippin parts on the car it is basically new under the hood. The car is driving fine though along with the wideband giving me normal readings :mad: I don't understand!!!
 

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A completely wild guess...

Have you checked to make sure you are not losing fuel between pump and rail (i.e. a slow leak)? Especially since it seems that you have good indications of engine performance, a leak of fuel would definitely contribute to poor MPG.

John
 
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