Cats holding heat- decrease in mpg's? - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 01-25-2011
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Cats holding heat- decrease in mpg's?

hey all,

firstly, truck details... 2002 4x4 SOHC AUTO

so i have noticed over a good amount of time now that my cats are holding heat...alot more than normal. i have knocked the last one out(the one without an 02) but im certain its not the issue. i have been getting less than great mileage out of it lately, been pulling about 210-230 miles to a tank, usually get a better read out than that lol. i pulled plugs today and checked, all seem to be just fine, but will be getting replaced fairly soon, so no un burnt fuel in the cats, and im not losing any oil...so its not being burnt either... that said. im at a loss of ideas.

post up your ideas and thoughts.

thanks guys
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Old 01-25-2011
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plugged?
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Old 01-25-2011
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Bad o2's?
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Old 01-26-2011
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plugged?
thats what im trying to figure out lol
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Bad o2's?
no codes
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Old 01-26-2011
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pull the 02 sensor out, and let it run with it out for a few, then check it. it'll have an extra hole to breathe through.
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Old 01-26-2011
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pull the 02 sensor out, and let it run with it out for a few, then check it. it'll have an extra hole to breathe through.
i don't think the 18mm hold will be enough... thats less than 1". i would rather test my 02's and eliminate that possibility. just unplug and run...


any other ideas?
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Old 01-26-2011
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only thing I ever heard was just unscrew it, and see if that helps. I think it might be enough, depends on how bad it might be plugged up. you can hook a gauge up to your vac lines if you don't want to try the o2 thing.
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Old 01-26-2011
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i was thinking that too... right now its a crap shoot...even if there is a problem
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Old 01-26-2011
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If they are plugged seems like the truck would be running bad too.

How do you know they are actually hotter?
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Old 01-26-2011
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what is the life expectancy of the O2's? And if the cats are high flow out of the factory, what would clog them up?
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Old 01-26-2011
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If they are plugged seems like the truck would be running bad too.

How do you know they are actually hotter?
thats what i would guess too... as for knowing its hotter... you can smell heat. i thought it was my trans for a while, but i checked that out. i was out cruising the mtns one day, and stopped and checked it out more (right after i checked the trans, checking on it) and could feel the high heat coming form it. more than the other
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Old 01-26-2011
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well they will become plugged. you wont want to know the price of factory cats though. Id recommend looking into magnaflow hi flow cats.
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Old 01-26-2011
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im considering popping them and clearing them and doing the defouler mod...... i don't have emissions here so it not such an issue. however, i wont do it unless that IS the issue
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Old 01-26-2011
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im just guessing, i mean there isnt any thing else i can think of that would make them hotter. maybe bad fuel?

i am not sure if i would unplug them, not without the proper tuning.
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Old 01-26-2011
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The only thing that can cause the cats to go bad is excessive fuel being dumped into them, making them overheat and either blow up or melt down and clog.

If there is no CEL, I would start by scanning it for any pending codes. Failing that, I'd suspect an upstream O2 sensor starting to fail, or react slowly (usually sets a code).

How many miles are on the vehicle?
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Old 01-26-2011
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im just guessing, i mean there isnt any thing else i can think of that would make them hotter. maybe bad fuel?

i am not sure if i would unplug them, not without the proper tuning.
if i unplugged them zach it would be to diagnose the 02's being bad or not, see if it throws a code

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The only thing that can cause the cats to go bad is excessive fuel being dumped into them, making them overheat and either blow up or melt down and clog.

If there is no CEL, I would start by scanning it for any pending codes. Failing that, I'd suspect an upstream O2 sensor starting to fail, or react slowly (usually sets a code).

How many miles are on the vehicle?
truck has 143k i did have an issue a while ago with the double code p0171 and P0174, both banks running lean. that caused by the illusive rubber hose breaking that does a 90deg. bend into the intake causing unmetered air into the system, in witch the truck dumps massive amounts of fuel in to try and counter act that... i had that for about 4-6 months... hard one to track down... so its possible it has caused the break down of the media in the cat. only catch is power wise, its fine. its still got really good power and pulls hard and smooth through the rpm range.

im still slightly stumped
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Old 01-27-2011
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If you drove it for awhile with that vacuum leak, it can roast the cats.

It will either melt down and clog up, making it nigh impossible to get over 30MPH, or blow out and start rattling. I have seen the catalyst get into the muffler, making it necessary to replace that as well.

I'd wait until it does one of those two things, as there's no need to replace it while it is still functioning.
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Old 01-27-2011
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Yeah, but he has a new (to him) muffler.

I've felt the heat coming off of his Cat's, and they get HOT. like, way hotter than mine ever did. My mom's van had a similar problem a while ago, and I think it's prettymuch gone away on its own now. but it never effected her mileage. (also have to remember that were talking apples and oranges here. Just tossing stuff out.)

On the flip side, Zach has a point with "If the cats are clogged, wouldn't the engine run rougher?" Also I'd think that there would be a lack of power, which there definitely is not...


Dan, maybe go through and inspect all the air hoses, and run some injector cleaner through it.

Could it be running slightly rich? Not rich enough to have the exhaust smell like gas, but rich enough that not all of the gas is being burnt in the cylinder, so it's burning up in the Cats, which would make them hotter. That would also effect your mileage.
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Old 01-27-2011
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Wirelessly posted

Seafoam!
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Old 01-27-2011
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Wirelessly posted

Seafoam!
....wouldnt help this situation at all
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  #21  
Old 01-27-2011
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...
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  #22  
Old 02-02-2011
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O2s, my favorite...
I've seen them fail completely with no codes, the heater codes seem fairly reliable, but not the "O2 failed" - usually these go at 50K (getting slow), that being said, I've got 135K on the OEM piece in my Focus that is just fine (a little slow, but good). I see more Bosch failures than Motocraft.
Hot cats is usually feul dumping as Murphy pointed out.

One customer got 3 $29 Bosch O2's from FeeBay (one at a time!) and all 3 were bad with NO codes (STFT and LTFT ROCK solid at "1") - put in a $75 OEM Motorcraft and problems were all solved. Good times...
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Old 02-02-2011
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Quote:
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O2s, my favorite...
I've seen them fail completely with no codes, the heater codes seem fairly reliable, but not the "O2 failed" - usually these go at 50K (getting slow), that being said, I've got 135K on the OEM piece in my Focus that is just fine (a little slow, but good). I see more Bosch failures than Motocraft.
Hot cats is usually feul dumping as Murphy pointed out.

One customer got 3 $29 Bosch O2's from FeeBay (one at a time!) and all 3 were bad with NO codes (STFT and LTFT ROCK solid at "1") - put in a $75 OEM Motorcraft and problems were all solved. Good times...
Was his name mark? lmao
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