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Inline 6 horrible gas mileage and low power?

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Old 03-08-2010, 07:12 PM
chevyassasin chevyassasin is offline
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Inline 6 horrible gas mileage and low power?

I just bought a 87 f150 with the ole inline six and auto tranny. i knew it had this problem when i bought it (it was really cheap, that's why i bought it), but i don't know what all could be wrong. I figured maybe the cats were cloged but i can't work on it yet due to it bein at my aunts house which is very far away. But anyways it's gettin about 8 miles to the gallon and it don't have much power. What all could it be?
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Old 03-08-2010, 08:16 PM
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Just a stab in the dark...

Before jumping into the "replace a bunch of sensors" diagnostic approach that many are fond of, ensure that the basics are in order. Ensure that your plugs, wires, cap and rotor are ok on the ignition side of things, make sure the thermostat is ok and the proper temperature, make sure the air filter is clean, and the fuel filter is good (also be sure to check your fuel pressure).
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Old 03-08-2010, 08:47 PM
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SideWinder4.9l SideWinder4.9l is offline
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Um, first off its a 300 I6, its not a fire breathing monster.....But seriously, My truck is a 94' w/ I6 & Auto and I get 13-15mpg around town.....Also its 2wd, but as soon as I got my truck I did the regular tune up; Plugs, Dizzy cap and rotory button, oil change and air filter, new HD Thermostat w/ upper and lower radiator hoses.....And VOILA! It clicks and clucks along like a charm....Also just got a new 2 1/4" exhaust from the rear catalytic convertor back.....It helps, trust me-

-Wes
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Old 03-09-2010, 10:04 AM
chevyassasin chevyassasin is offline
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Originally Posted by SideWinder4.9l View Post
Um, first off its a 300 I6, its not a fire breathing monster.....But seriously, My truck is a 94' w/ I6 & Auto and I get 13-15mpg around town.....Also its 2wd, but as soon as I got my truck I did the regular tune up; Plugs, Dizzy cap and rotory button, oil change and air filter, new HD Thermostat w/ upper and lower radiator hoses.....And VOILA! It clicks and clucks along like a charm....Also just got a new 2 1/4" exhaust from the rear catalytic convertor back.....It helps, trust me-

-Wes
I'm guessin that the fire breathing monster comment was saying i thought the 300 had tons of power. lol. I know they don't cause i've had 4 300s, but it's got nothin.How many mpgs were you getting b4 the tune up?
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Old 03-09-2010, 10:11 AM
chevyassasin chevyassasin is offline
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I think I'll start by looking at all the ignition, fuel, and air basics to make sure they're right, take the cats off (i'm puttin an exhaust on anyways), then start to replace sensors if none of that helps. I hope this don't cost me more than the trucks worth!!! lol
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Old 03-09-2010, 10:36 AM
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I'm going to suggest you do some investigation before you spend a dime on parts. First thing to determine is if it has dual tanks and if they both work and if there is a fuel transfer problem between them.. which is real common. If it does have this problem then the active tank is overflowing the other and dumping fuel on the ground as you drive. Also check fuel pressure and for the presence of fuel in the vacuum lines attached to the fuel pressure regulator and throttlebody. If all this checks out then pull the codes to see if anything is flagged and fix those issues, and then do a tunup with new filters and fluids.
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Old 03-09-2010, 08:02 PM
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No ChevyAssassin....It was some of the off key humor I have....Any way...On the Pre-Tuneup MPG's, I couldnt honestly say, I only had the truck like 3 days to a week before the tune up....So I honestly dont know...Maybe some one can help me with this lil problem I seem to have accrued; I took my dash cluster out, swapped the clear lights for red ones, and took the gauge needles off and scraped the green film off so they show up bright, and now they seem to be off a bit...What would be the best way to reset them? I thought about letting the truck cool completely, and resetting the TEMP gauge to nothing, and the VOLT gauge allas ran about midways.......Any help will be greatly appreciated...Also, the speedo is still dead on...So IDK..


Thanks all-

-Wes
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Old 03-09-2010, 10:57 PM
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its not too full of oil is it?
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Old 03-09-2010, 11:07 PM
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Quote:
Originally Posted by SideWinder4.9l View Post
No ChevyAssassin....It was some of the off key humor I have....Any way...On the Pre-Tuneup MPG's, I couldnt honestly say, I only had the truck like 3 days to a week before the tune up....So I honestly dont know...Maybe some one can help me with this lil problem I seem to have accrued; I took my dash cluster out, swapped the clear lights for red ones, and took the gauge needles off and scraped the green film off so they show up bright, and now they seem to be off a bit...What would be the best way to reset them? I thought about letting the truck cool completely, and resetting the TEMP gauge to nothing, and the VOLT gauge allas ran about midways.......Any help will be greatly appreciated...Also, the speedo is still dead on...So IDK..


Thanks all-

-Wes
Are you saying that the gauges are reading correctly? How far off are they? There isnt any way to reset the cluster that i know of. But i think you probably got a loose connection somewhere when plugging stuff in.

And also, when you put the cluster in did you make sure that non of the gauges where out of range? when i was messing with mine once, i didnt notice that one of them got pushed past where it could recenter it self and had to take it all apart again to fix it.
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Old 03-10-2010, 01:26 AM
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Quote:
Originally Posted by Argo View Post
Before jumping into the "replace a bunch of sensors" diagnostic approach that many are fond of, ensure that the basics are in order....
Quote:
Originally Posted by Conanski View Post
I'm going to suggest you do some investigation before you spend a dime on parts. First thing to determine is if it has dual tanks and if they both work and if there is a fuel transfer problem between them.. which is real common. If it does have this problem then the active tank is overflowing the other and dumping fuel on the ground as you drive. Also check fuel pressure and for the presence of fuel in the vacuum lines attached to the fuel pressure regulator and throttle body. If all this checks out then pull the codes to see if anything is flagged and fix those issues, and then do a tuneup with new filters and fluids.
Bolding mine.

What these wise individuals said! ^^ Test don't guess! A quick check of the basics will save you a lot of trouble.

What you describe sounds like something I have encountered before on these trucks. I have replaced a number of fuel pressure regulators on the fuel injected sixes. Don't know what it is about this model. A check of the fuel pressure is definitely one of the first things to verify. With a bad regulator you can see well over 100 lbs of fuel pressure! They will run, but not well. It may also run for a couple of minutes before teh pressure goes batty on you. If that is the problem make sure you change your oil also because it will be full of fuel.

Recap: Check the basics and go from there!
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Old 03-10-2010, 09:35 PM
chevyassasin chevyassasin is offline
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Thanks guys. i'll start on it when i get the truck here
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Old 03-11-2010, 12:47 AM
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yeah i need to replace my plugs and wires, but definately change the exhaust, i would be careful touching the cats if you like your low end power, but a new muffler helps alot

i also have a k&n drop in filter, it seems to help but im not sure if the pain of cleaning it is worth the amount it helps quite yet haha
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Old 03-11-2010, 04:20 PM
chevyassasin chevyassasin is offline
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well i won't have to worry about this truck anymore, i just traded it for a newer (95) f150. Thanks so much though guys!
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Old 03-11-2010, 06:52 PM
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I get 9-10 mpg on a good day. I'm going to get high performance plugs, wires, dizzy cap, rotor, and a coil, then I'm going to do a timing bump! Before all of that, I'm going to Seafoam my truck. I'd be tickled pink if I got 13mpg after all that.
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Old 03-11-2010, 11:49 PM
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i get 11.4 on a good day...mind you im turning 35s with 3.55s gears ...truck got roughly 15 before the lift/tires....not to mention the *******s that did the inspection on my truck topped up the rear diff with something like 130 weight oil? gotta change that back out for 80-90 then i might get some MPG back
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