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Discussion Starter #1
My 98 4 cyl Frontier currently gets 28 mpg (145,000 miles on it)
My 2004 4 cyl Frontier only gets 13-16 mpg (45,000 miles on it)

WHAT Happened there?

I bought the '04 used in 06 with 35,000 miles on it...
has 45k now.
I ensure the tires are inflated,
New dist cap and rotor- didn't like the looks of the dist/rotor when I opened it up.
new air filter (was fairly clean anyway)
Fuel injector clean- no significant increases with any of the above. Engine appears to idle smoothly

Any other suggestions?
This truck is a bit more noticeably sluggish from a standstill and accelerating than the 98.

I am thinking checking plugs again and wires

Local Nissan Dealer had no suggestions for me..

Certainly I can't blame it all on wider tires on the 04!

Hell with 13-16 mpg I could be driving a 6 cylinder SUV!!
This was a disappointing surprise
Thanks
 

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many things can cause poor mileage. yes, even one built on a Monday or a Friday. My mother had a 98 olds 98 brand new which got 28 mpg city. 4 wks after purchased it was totaled. replaced it with another identical vehicle to the color and it got 24 mpg in the city.

could be a weak coil, poor plug wires, bad fuel filter, even the ECM could cause this. you might even look into seeing if there were any ECM updates for the 04.
 

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Discussion Starter #3
I've had experience with bad wires on the 98- bucking engine during certain speed ranges. What symptoms with a bad coil?
(BTW fuel filter is also new- I do it every year and it figured it was part of the lack of zip.... when I stepped on the gas...compared to the 98 frontier)
 

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poor gas mileage is a sign, how do you test them, got me. I know a good coil can create a long, bright spark when you have a plug removed. you could also look at the MAF sensor see if it needs to be cleaned. I'm just throwing ideas out there on what I would look at. do you have a fan clutch, if its bad it could put an extra load on the engine, dont know if it would affect the mpg that much though.
 

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Something is definently not right.
I average 21 to 22 mpg in the summer ,and thats with consistent towing of my jetski.
I have 49k ,and have yet to change any ignition parts.

The 04 most certainly has the computer much more involved on how it drives vs the 98 despite them having the same rated power.
Sometimes my 04 feels great off the line ,and other times its very sluggish as if the computer is pulling fuel.

Its been this way since new.
I think they have it programed to squeze every mpg they can out of it.
 

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Have the exhaust system checked for obstructions by a competent muffler shop. They can check for excessive exhaust backpressure which would indicate a clogged cat/muffler or some other problem.

Sure sounds like it could be something like that, since you're not only having poor mpg but are down on power too.

Other things that could be checked are the O2 sensor and Engine Coolant Temperature sensor (ECT or ECS, not sure what Nissan calls theirs!).

These sensors may be out-of-calibration and messing up engine operation, but not be bad enough to cause a trouble code.

Sure seems the Nissan dlr should have sophisticated enough diagnostic equipment to figure out your problem! Maybe it's time to consult another dealer, or an independent specializing in E.F.I. tuning/troubleshooting.

Also seems that a problem which causes you to lose 15mpg or more would cause much higher emissions, surprising the Smog Cops haven't caught up with you!

Got to echo the comments on the '98 Frontier, my 2WD KC gets around 28-29mpg on a medium-length hiway trip. Never had it on a long trip, I'm sure it'd do 30 or more. Great truck!

HTH & let us know what you find..........ed
 
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