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Discussion Starter · #1 ·
i have an 04 canyon 3.5L. automatic..... lifted 2 in. suspension.... 3 in body lift.... 31 10 50s... but they are almost slicks.... new bosch platinum 4 spark plugs... cleaned maf and throttle body....changed oil and filter....changed fuel filter....new gas cap..... k and n intake.... cleaned k and n air filter and recharged it.... seafoamed through the intake hose....what gives.....i drove this whole tank easy tried to stay under 2000 rpms as much as possible...using cruise any chance given..... what is the problem????
 

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From what I have heard, platinum 4's do not work well in these Atlas inline engines. Everyone one recommends NKG/AC Delco Iridiums or Denso Iridiums...

Also, poor mileage is one of the symptoms of a bad head. In your year truck, the valve seats in the head were not properly hardened and are prone to premature failure. Are you showing a check engine light? Is the truck idling rough or misfiring?

Also, clean your MAF sensor again. Oil from a freshly oiled K&N can foul it very quickly. Make sure you use a MAF sensor cleaner like CRC MAF Cleaner and do not touch any of the wires or thermistors. Spray the shit out of it and that's it...
 

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Discussion Starter · #3 ·
ok ill try new plugs sometime soon....... but at idle it seems smooth....it doesn't mis or anything.....by misfiring do you mean at startup? sometimes not often though i noticed it takes like 5 seconds longer to start up but then starts fine and runs fine....
 

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Discussion Starter · #6 ·
may be a slight possibility but ive never gotten good gas mileage out of this truck had it five years....ive seen ppl say on here there gettin upwards of 28 - 30 mpg...something has got to be wrong...
 

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What size are your stock tires? How are you calculating your MPG? Are you accounting for your speedometer inaccuracy's because of a potential tire size differential.

I've also heard of the Bosh plugs not being the preferred. I don't know what the negatives are though, just heard they aren't the preferred.

Is your K&N filter over oiled and now your MAF has an oil coating on it returning poor readings to the computer?

Your 5" lift sure isn't helping your aerodynamics either. Do your wheels stick out far? That changes the aerodynamics too. The 10.5" tire doesn't exactly slice through the wind either. May not be very negative though, compared to the stock tire size.

Yes, 13.5 is low but right now that number may be void since we don't know for fact that you are calculating properly. A proper calculation could raise it by 2mpg, which would then be about right for the modifications you've done.

Staying under 2000 rpm may not be key either. When you load up the engine with a low rpm, you are jamming your foot down further than at higher RPM dumping in more fuel.
 

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Dam Im running corrected Scan gauge II / GPS to double check and I thought with my 3.7 2012 getting 18.7 mpg avg / 21 hwy with my new 32"'s lifted 4" was bad from 20 avg and 24 hwy . The 32's killed my mpg more than the lift . I drive my truck like a old lady , but ride my bikes like there is no tomorrow .

That pic is with stock 31"s

 

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The plugs, gas and speed being off are all contributing to the poor mpgs.

Have you O2 sensors even been replaced and how many miles are on the truck. Anytime someone has issues here they automatically say the head issue...........99% of the time that's not the issue.

When was the last time the trans filter and fluid were swapped, rear diff fluid, front diff fluid and so on. Has the cam actuator valve ever been replaced .......I can go on. I've had my 04 3.5 since new so I know a bit about them and the things to get the mpgs

Over the weekend I was only getting 25.2 MPG on a road trip.....which is down from a 27-28 MPG norm. Its the gas on my end.
 

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ya something has to be wrong. i have about 9" of lift, 35"s that weigh 105lbs each, and im still getting about 15 with a misfire code throwing. do you have either cat removed? if so i would get it tuned, when i was on 33"s i gained 4mpgs with a tune. was wasting fuel with the stock settings and no cats
 

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Discussion Starter · #13 ·
ok replaced the cam actuator solenoid about 100 miles ago just because i had read it may affect it.... never changed trans or diff fluid or filters.....i put a new upstream 02 in about a month ago trying to resolve issue didnt help.....got 145000 on the truck...
 

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ok replaced the cam actuator solenoid about 100 miles ago just because i had read it may affect it.... never changed trans or diff fluid or filters.....i put a new upstream 02 in about a month ago trying to resolve issue didnt help.....got 145000 on the truck...
ouch

mines has 150k, and I changed transmission fluid every 30k
 

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Agreed on changing the fluids.

Cruse control does not always get you more MPG's. If you are going up and down hills a lot it is better to turn it off, on flat it is better to use the cruse control.
 

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Only to repeat what's been said already, check your speedo accuracy. What size tires were originally on the truck? Was the PCM ever updated after (I'm assuming) the larger tires were put on?
 

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Discussion Starter · #18 ·
Yes I know I am using the wrong calculation but it can't be off by much... It's a crew cab 4x4... Not sure what size stocks were... But I have 31 10 50s on it.... Even with the right calculation I could only see like a maximum of 2 more mpg which would put me at 15 mpg which still sucks compared to the guys that are gettin 20- 23 and even saw 28 somewhere... I think its more than just the speedo calculations guys...... Do you think having the fluids changed would make a difference???? I'm open to any help


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Discussion Starter · #19 ·
I Still have both cats on it.... Hasn't been tuned.... I use 93 octane all the time.... I put a new tstat on it 500 miles ago...... ABS system doesn't work but I wouldn't see that contributing to bad mpgs.....also the k&n intake I'm using came off of a 09 Colorado so it didn't exactly fit right.... The Maf sensor is siliconed in and it sits at a little bit of an angle instead of being straight with the pipe..... Could that be an issue???? Also that intake didn't have. Place to hook the fuel pressure regulator so for about a year it has been just hanging in the wind until the other day I drilled and tapped a hose barn into the intake tube to hook the fuel pressure regulator up to... I did it and it sealed up good but really didn't notice a difference with it hooked up or not????? Could it be bad since it was open to the air for a year ????? Need help lol


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I get about 17 mixed and have 31 10.50 on my truck but am stock height. You say that your calculations are off, but not much. could they be off enough to be 1-2 mpgs off? I assume you have 3.73 gears (as do I) but, maybe you have 3.42s and the 31's might be a bigger culprit than being suspected. There is no reason to be using 93 octane unless you have atune that requires 93 octane. I run 93 octane every few months to help clean the fuel system and notice my mpg are usually worse by 1-2 mpg but, I am also running seafoam in the tank and that may also rob the mpgs. That could be the culprit, plus you are wasting your money.

Anyways - good luck and let us know what you find.
 
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