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90 CRX Si
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3,866 Posts
Discussion Starter #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.
 

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90 CRX Si
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3,866 Posts
Discussion Starter #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
 

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92 cx
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934 Posts
Well youd get bad mileage if your pump wasnt pumpin enough pressure when u put the throttle down, kinda like a leaky fuel injector or bad injector would also give u bad mileage.
 

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90 CRX Si
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3,866 Posts
Discussion Starter #5
That's what I was thinking, but i figured it would lean out the AFR's and I'd be able to see it on my wideband. If anything, it may be a bit richer than it used to be.
 

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92 cx
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Maybe if u got free time go under the car check ur fuel lines make sure none of them are pinched from random chit. Other than that im bad with electronics. Good luck.
 

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90 CRX Si
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3,866 Posts
Discussion Starter #8
Its called get that loan and build the motor lol,Change out that pump i bet that will help.How long you say it has been going on for?
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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