Why am I only getting 200 miles per tank?

Suggestions besides plugs? Stock fuel pump with 127k @ 32-35 psi at idle.
 
NoLimit95 said:
That pressure sounds correct. As cheap as plugs are, it couldn't hurt to change them. I use 764's myself but I think my next swap is going to be Motorcraft Platinum. I average around 16 with the 764's
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You think the 12c's "two steps colder stock" than are too cold for winter, not getting up to temp?, also the chip keeps the car cold all the time.
 
I can tell you that I regularly got 10 mpg running errands in stop-n-go traffic in my Aviator. It's the number one reason I couldn't hack having it. That being said, I run alot of errands in my 97, 62K miles, and rip around some of the time and was averaging about 12. Now that I'm in cruise mode more often, I'm close to 17 with mostly stupid, in town stuff. I also put NGK Laser Iridium plugs in. Coincidence? I dunno.
 
Yeah that's another huge factor..

Do you have an accelerator pedal, or an On/Off switch?
 
What size "new" fuel injectors?
Or should I say hose pipe?
Any codes?

Kill the tune, check codes.....you have a major issue.
Any leak that bad you would smell a mile away.
 
I would say your compression is down on some of the cylinders, and the gas is not getting a clean burn. Compression test all of your cylinders.
 
Years ago when I drove it hard I'd get down to 13mpg 100% city driving. Now I average 21mpg 80/20hwy with a very light foot.

Start with disabling the tune, then move onto filters, plugs, clean maf ect. Cheap stuff that could have a big impact on your mpg issues.
 
Dennis reinheart advised me to use 12c's in conjuction with the chip. I'm going to swap out the ecu, install stock plugs and see where I end up. For those of you saying comp isseus it's a brand new motor.
 
quickblue302 said:
Dennis reinheart advised me to use 12c's in conjuction with the chip. I'm going to swap out the ecu, install stock plugs and see where I end up. For those of you saying comp isseus it's a brand new motor.
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New motor meaning? I run Autolite AR94 which are I think 2 steps colder. I have been running them for 6 years.
 
Meh. New don't mean jack. Maybe they built it wrong. New cars roll off the assembly line that won't start all the time. New doesn't mean good. I'm not saying its bad. But new doesn't mean good.
 
How are you putting 18+ gallons to the tank? Are you just using the tank capacity of the mark viii from the manual? The most I've filled is 14.8 and this is almost empty. Is it an original tank?
 
Hot*Mk8 said:
Thaywood, I also have some good coils if you find that you need more than one. :D
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Thanks! I appreciate that. It's 40 degrees and raining today so I doubt I'll be able to install the new coil until later in the week. Probably Friday. I'll let ya know. Live long and prosper!:)

Oh BTW, love your new sig pic!!!

93mkviii said:
How are you putting 18+ gallons to the tank? Are you just using the tank capacity of the mark viii from the manual? The most I've filled is 14.8 and this is almost empty. Is it an original tank?
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Yep. The Mark VIII is supposed to only have an 18 gallon tank. Theoretically it should be impossible to put more than 18 gallons in it even if it is completely dry. I suppose if it's totally dry and you fill the tank and the filler tube all the way up the neck, you might be able to get 18.5 gallons in it. I think the most I've ever put in mine was about 16.5 gal and I was quite literally running on fumes.
 
My father tracked mpg for the first 100K on my 93 Mk8. Combined was about 20 mpg. I started tracking again at abt 200K still getting the same. No mods. I ran it down to "10 miles to empty" today and put in 17.5 gal. Have never put in more than 18 gal. When I drove it home from KC in March I got 25-26 mpg. I know nothing about mods :(. Hope you get that sorted out.
 
I'd love to be able to use non-ethanol premium gas in mine. But I can't find a gas station within 3 counties that has anything more than 87 octane "pure" gas. And it's about 20 cents higher than the 10% ethanol blend everybody else uses. :(
 
thaywood said:
I'd love to be able to use non-ethanol premium gas in mine. But I can't find a gas station within 3 counties that has anything more than 87 octane "pure" gas. And it's about 20 cents higher than the 10% ethanol blend everybody else uses. :(
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Marinas. Boats don't use ethanol fuel because it's bad for their engines. You pay more, but you can get 100% gasoline with 0% ethanol.
 
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