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SmokinVette.com Forums : Corvette Forums : C4 Corvette Forums : C4 Tech & Performance : MPG Question
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Old 03-01-2012, 07:34 AM   #1
Rain37
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Default MPG Question

I have a 84 Vette with the crossfire injection. It's my dad's but it's pretty much mine now.
Anyway it's been sitting for the last two years because it developed a pretty nasty miss and with the work my dad does he didn't have time to fix it. So he parked it in our barn with intentions of eventually getting it running again. So on sunday with me getting board with my truck, I putted the Vette out and changed the plugs and wires. Fixed the miss. The MPG went from 12 to 18. I did some research and found that this year should get 22-26 MPG.
Does anyone have any ideas about what I should do, fix, rebuild, or replace to get it some better MPG? It has 182,000 miles right now and it is my daily so I know a few things needs to be done to it.
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Old 03-01-2012, 08:23 AM   #2
500hp406
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With that many miles you should consider replacing/cleaning the two injectors.
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Old 03-01-2012, 09:11 AM   #3
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With that many miles you should consider replacing/cleaning the two injectors.
I will try to do that. Do you know where I can find a how to for that? I have never replaced those on a car before.
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Old 03-01-2012, 09:29 AM   #4
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they are very easy to replace..Do you have a FSM? Google for a place that is close to you that rebuilds those injectors..
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Old 03-01-2012, 09:44 AM   #5
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Default Bad Fuel Mileage 1984

Quote:
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With that many miles you should consider replacing/cleaning the two injectors.

My injectors have 285,000 miles on them and have never been any trouble. If his fuel mileage is that bad he may have a leaking injector o-ring or gasket (assume his engine has been properly timed and the TPS correctly set and the O2 sensor is still good). Or he might even have a bad MAP sensor or hose going to it.

I suggest taking the air cleaner off first and see if there's any sign of fuel leaking from the injectors while the engine is idling. If so then he'll have to fix whatever is wrong.

Oh yeah, and that 25 mpg will ONLY happen on a flat highway in 4th gear. Around town the mileage will be only 1/2 of that.
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Old 03-01-2012, 03:06 PM   #6
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Whats the coolant temp? To me anything below 185* on the gauge while going down the road is too cool. Coolant temps greatly effect mpg on efi cars.
Check the ign. timing.
Check the connection at the cts, the early ones (like on your 84) are troublesome. You can upgrade to a later cts & connector.
It might take awhile for the mpg meter to get high, what kind of driving do you do?
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Old 03-01-2012, 03:55 PM   #7
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Quote:
Originally Posted by ex-x-fire View Post
Whats the coolant temp? To me anything below 185* on the gauge while going down the road is too cool. Coolant temps greatly effect mpg on efi cars.
Check the ign. timing.
Check the connection at the cts, the early ones (like on your 84) are troublesome. You can upgrade to a later cts & connector.
It might take awhile for the mpg meter to get high, what kind of driving do you do?
My temp usually stays around 172 to 186. I usually do highway driving and it usually at the speed limit or just a tad under.
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Old 03-01-2012, 04:18 PM   #8
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Get a good quality t stat. 195* is stock. That'll help bring up those numbers.
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Old 03-02-2012, 07:26 AM   #9
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Quote:
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Get a good quality t stat. 195* is stock. That'll help bring up those numbers.
T Stat?
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Old 03-02-2012, 03:17 PM   #10
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Quote:
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T Stat?

That's the lazy way of saying T H E R M O S T A T

Yeah, to run right you need to have a 195 degree thermostat in it so your coolant sensor will send the correct voltage to your computer.
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