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Bad fuel mileage

696 views 9 replies 3 participants last post by  xotic_crx 
#1 ·
Guys i've been having a problem lately of bad gas mileage. Its been as low as ~20mpg over a tank, and no higher than 28-29 and that was all highway. Usually my car makes in the mid 30's, high 30's on highway trips.

Fuel filter is recently changed, plugs and oil about 3 weeks ago (old plugs looked ok, just had carbon buildup on the outer metal like the threads), my A/FR's seem normal on my LC1, WOT is around 13:1 all the way across and cruise is between 13.5:1 under load to 16:1 in very light load.

I don't smell any gas, and I can't find any leaks under the hood, BUT I am losing pressure rather quickly once I key the car on w/o starting it. Its a stock pump, RC 320 injectors, and AEM FPR on stock rail. B&M pressure gauge on the filter is where I'm seeing pressure fall from 45 to 20 within 10-15 seconds, then slows.
 
#3 ·
:oops: Yeah I've had a walbro 255 hp laying around for quite some time, i just haven't put it in. I know the pump could cause the pressure to drop, but what about the mileage. It does kinda feel like I have to keep my foot in it a bit more than before, especially at lower RPM's
 
#8 ·
I know, i keep going back and forth on whether or not I should do it. Anywho, its been going on for probably about 2 months

Oh and BTW, my compression is down a bit from 4 months ago, it was
#1 - 203
#2 - 202
#3 - 205
#4 - 205
This was right after i almost killed it by sucking up some water.


Now its
#1 - 203
#2 - 190
#3 - 190
#4 - 205
 
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