bad gas mileage?

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[TurboSedan]

my Regal is getting really shitty gas mileage and the only thing i can think of is it being due to the WAI (cone filter on the end of the F-duct).  the needle drops like a rock and the DIC used to read 21-22/city but now it's around 15.8-ish.

does a WAI usually hurt gas mileage like this or could it be something else?  the car is running great but it sure is thirsty.

[mfewtrail]

Has the boost bypass valve been adjusted on it Josh? My car was getting some pretty shitty mileage w/ the bypass valve adjusted to get into boost quicker(I would have boost @ very light throttle just pulling up slight grades). Throw the stock airbox back on the car and see if it helps. A HAI really slows down the car if you let it idle for a while and then romp on it.

[TurboSedan]

Has the boost bypass valve been adjusted on it Josh? My car was getting some pretty shitty mileage w/ the bypass valve adjusted to get into boost quicker(I would have boost @ very light throttle just pulling up slight grades). Throw the stock airbox back on the car and see if it helps. A HAI really slows down the car if you let it idle for a while and then romp on it.

i don't think Dan did anything to the BBV, as far as i know the only change is the WAI.  i'm gonna throw the stock airbox in tomarrow.

[sl3196]

Like I said that thing never got good mileage for me even with the stock airbox.

[TurboSedan]

Like I said that thing never got good mileage for me even with the stock airbox.

it's way worse now then when i had it before; it's gotta be the WAI (probably fucking with the MAF on stock PCM?).  when i was delivering pizza with the car the average MPG was always 21-22mpg.  it even got about 31mpg on the highway on a trip to Denver (when i picked up the GTS last September).  ever since i've had it back it's been 15.8-ish average every time i've looked.  i'm not sure what highway mileage is now but hopefully with the stock airbox back in there it will still be ~30-31mpg.

[sl3196]

Hmm maybe.  Guess I traded it back to you the same day I put on that intake haha.

[TurboSedan]

i just put the stock airbox back in.  SC is alot quieter now and it doesn't seem to pull quite as hard but hopefully gas mileage goes back to what it was.

i think i have your old F-duct.

[TurboSedan]

i think i might have found the problem.  lately i've noticed the temp gauge has been reading lower than normal but i figured it was just because of winter temps.  but the heater also seems to take a long time to get the interior warm.  thermostat partially stuck open?  that happened once with my Cutlass a few years ago - the thermostat was actually ripped wide open!

i have a new thermostat to put in (forgot the what temp it is - Dan bought it).  still need to go get a gasket though.

on my trip to MN last week the car only managed 24.4mpg/hwy on the way there and a measly 22.4mpg on the way back.  granted that was with a loaded down car (enough that the rear end was sitting pretty low) but jeez that still SUCKS!

[SlowGTP]

yeah...that milage definatly SUCKS!...if dan got it, its prolly a 180*...

[sl3196]

yeah...that milage definatly SUCKS!...if dan got it, its prolly a 180*...

Yup haha.  I still get 28-29 on the highway with the GTP though.

[SlowGTP]

yeah...that milage definatly SUCKS!...if dan got it, its prolly a 180*...

Yup haha.  I still get 28-29 on the highway with the GTP though.

yeah...i can still pull 29-30mpg on the highway if i fill up right before i get on the highway...

[TurboSedan]

well Dan and i scanned with his LS1M last night and coolant temps were normal....staying around 185-190*F IIRC...soo...the problem doesn't appear to be the thermostat.  however,  i am getting some pretty bad KR.  i forget how much, but Dan is going to post the scans on scandepot.net soon i think.  one of the runs was from ~20mph roll on i think.  i was going too fast for it to downshift into 2nd but held it in 2nd gear up to 90mph.  the 2nd run was the same but i was going slow enough that time that it downshifted into 1st then held it in 2nd again up to 90mph before letting off.  car just feels slow....and guzzles gas.

so basically the car is running fine, no codes or anything, but it's getting bad gas mileage and it feels slower than it used to.  when Dan had the car he put a cone air filter on the end of the F-duct and i thought that might be the culprit so i put the stock airbox back in - nope - still getting shitty gas mileage.  so i started thinking it was the thermostat but according to the LS1M all is normal there.  any ideas?  we scanned last summer on a 103*F day and i was getting practically NO KR at all and the car felt much faster.  there have been no changes to the car besides a fresh oil change using Mobil-1 10w30.  it is 100% stock - no mods whatsoever.

i know Dan ran Seafoam through the engine while he had the car but never replaced the spark plugs afterwards.  that's the only thing i can think of.  i guess i'm going to buy some new spark plugs and see what happens.

[99RegalGS]

clean the MAF maybe???

Seeing the scan will help a bit more though.  Hurry up Dan!!!

[sl3196]

http://www.scandepot.net/viewscan.php?pk=3252

http://www.scandepot.net/viewscan.php?pk=3253

[99RegalGS]

<@GSRegal99> CLSD
<@GSRegal99>    
<@GSRegal99> CLOSED-LOOP STATUS
<@GSRegal99> ECT
<@GSRegal99>    
<@GSRegal99> ENGINE COOLANT TEMPERATURE
<@GSRegal99> LFT1
<@GSRegal99>    
<@GSRegal99> LONG-TERM FUEL TRIM, DRIVER?S SIDE
<@GSRegal99> MAF
<@GSRegal99>    
<@GSRegal99> MASS AIR FLOW
<@GSRegal99> MPH
<@GSRegal99>    
<@GSRegal99> VEHICLE SPEED
<@GSRegal99> O2L
<@GSRegal99>    
<@GSRegal99> OXYGEN SENSOR, DRIVER?S SIDE
<@GSRegal99> RPM
<@GSRegal99>    
<@GSRegal99> ENGINE SPEED
<@GSRegal99> SFT1
<@GSRegal99>    
<@GSRegal99> SHORT-TERM FUEL TRIM, DRIVER?S SIDE
<@GSRegal99> TPS
<@GSRegal99>    
<@GSRegal99> THROTTLE POSITION