Getting horrible gas mileage from a v6...

[ThatChevyGuy 5,000+ posts]

I have a mountaineer with a 4.0 v6 and here lately its been getting 250 miles to the tank. I drive mostly highway miles back and forth to school. Im thinking it might be due to a clogged cat or something, i can smell rotten eggs when its sitting running and it smells like its running really rich. It has full intake and exhaust and is not throwing any codes. Im talking 12-14 mpg at best. Whats wrong? is it the cat? if so its about to get replaced with 3" pipe

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[whitedragon551 5,000+ posts]

Rotten eggs is the cat. Id also change spark plugs, wires, and fuel filter while your at it. Pretty cheap stuff and it goes a long way.

 

[ThatChevyGuy 5,000+ posts]

I forgot to mention i just tuned it up, cleaned iac and maf, replaced fuel filter, cleaned air filter, ran some injector cleaner.

 

[jco1385 5,000+ posts]

plugs, wires, coil packs. clogged cat, bad o2's... if you take out the cat, you'll need to get a tune or it will be worse. w/o the cat, your o2 will throw a code, and it will run really rich/lean ( i forget which //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif)

 

[whitedragon551 5,000+ posts]

plugs, wires, coil packs. clogged cat, bad o2's... if you take out the cat, you'll need to get a tune or it will be worse. w/o the cat, your o2 will throw a code, and it will run really rich/lean ( i forget which //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif)

Unless he puts an O2 bung on the pipe and puts the O2 sensor back in. He could also do an O2 simulator which just plugs into the O2 sensor, but never goes back into the actual bung.

I would just change the cat and replace plugs and wires and call it good.

 

[jco1385 5,000+ posts]

well the o2 would still get a bad read, which was my point. i run w/o cats and i have an SCT chip and tune.

 

[ThatChevyGuy 5,000+ posts]

oh im gonna run without a cat, i already have headers

ARKANSAS RULES

REDNECK FO LYFE YA DEEG

 

[jco1385 5,000+ posts]

no inspections ftmfw

 

[Johnny Law.Lulz 5,000+ posts]

Here in Va we can get an inspection without a cat but we can get a ticket for it still.

Id rip the cat off, run some lucas through every fill up for a little bit, also check your trie pressure.

 

[ThatChevyGuy 5,000+ posts]

im gonna replace 4 02 sensors after the shop does the cat delete, and do a dummy setup i guess if i have any problems. You'd think id be getting decent gas mileage with the mods, maybe its hurting.

 

[ThatChevyGuy 5,000+ posts]

Here in Va we can get an inspection without a cat but we can get a ticket for it still.
Id rip the cat off, run some lucas through every fill up for a little bit, also check your trie pressure.

tire pressure is at 35.5 on brand new tires. Which lucas? i have about everyone. I just seafoamed it not too long ago

I think i might have an INTAKE GASKET LEAK (AAAAAHH)

 

[jco1385 5,000+ posts]

cake job. pussy. do the HG's while you're in there.

 

[ThatChevyGuy 5,000+ posts]

well the o2 would still get a bad read, which was my point. i run w/o cats and i have an SCT chip and tune.

Where to get tune? I needs soon

 

[Louisiana_CRX 5,000+ posts]

i usually got between 350-400 miles to the tank out of my 99 V6 4.0 ranger but everything was stock

 

[jco1385 5,000+ posts]

well, i guess if you run a "dummy" o2, you might not need one. i'm guessing it's a sort of o2 simulator. i'm not too keen on them shits. i just dropped the $$$ on the chip for later tunage when i do more mods. i have the 3.8, and with tubular manifolds (basically headers), no cats, and dual flow 40's i still get 20-22mpg city/highway mixed driving. not too bad.