horrible mpg

[Jack Davis]

i have a 07 ram 1500 3.7. its not the clutch fan to start off with, just had to change that to cause it was bad to. im thinking its the cat cause when i bought the truck it had a check engine light on and they said it was a o2 sensor and they replaced it. keep in mind i bought this from a dealer. im getting around 10 mpg and i hear the rattle. no its not my driving i rarely go over 2300k

im wondering what would be better gutting the cat or going with the magnaflow 52291. if i gut it do yall think i would get better worse or about the same mpg. and i know my engine light would be on and i would do the bypass and i know its illegal gut or remove it.

 

[LoneWolf3574]

Does the rattle occur during acceleration from a standstill and sound kind of tinny? If it is, that would be one or both of your exhaust manifold heat shields and you probably have an exhaust leak on top of that. Also take into consideration that your gross weight is around 6600lbs, that is a bit of weight for a 3.7L (226cui) engine to move. Is it a 4x4? If so, is there a lift? How big are your tires? Are you running with all terrain tires instead of passenger? How many miles are on the truck? Do you have a CEL, if so, what codes? All these are things that may and can affect your fuel economy. Still, 10mpg is terrible for a 3.7L IMO.

 

[Jack Davis]

its a 2wd with 87k stock with 33 with no cel. it does it when i start it up and under acceleration but if i give it enough gass it goes away for a bit

 

[Wahrsuul]

Did they replace all the O2 sensors? I usually replace them in sets. They wear out over time, and if one is bad, the other(s) aren't far behind.

 

[Jack Davis]

I have no clue I will have to look tonight when I get home. Before I replaced the clutch fan I was getting 200 miles to the tank now I'm getting 250 miles a tank but I believe it should be more then that

 

[fastf]

How long have you owned the truck and did you get some kinda warranty from the dealer?If you did I would make him make it right.

 

[Jack Davis]

It had like a 90 warrant but I have had it for 4 or 5 months

 

[LoneWolf3574]

its a 2wd with 87k stock with 33 with no cel. it does it when i start it up and under acceleration but if i give it enough gass it goes away for a bit

Are you able to record and post the rattle you're talking about so other members can hear it and possibly help? I don't think it's your exh. manifold heat shields based on what you stated.

 

[fastf]

LoneWolf it sounds like his cats maybe on the verge going south but like you said without hearing what it sounds like we are guessing.

 

[Jack Davis]

so this morning went to leave and it was making the noise right off the bat. so i jumped out of the truck and noticed it wasnt the cat so i popped the hood and its pulleys just have to figure out with one.

 

[LoneWolf3574]

so this morning went to leave and it was making the noise right off the bat. so i jumped out of the truck and noticed it wasnt the cat so i popped the hood and its pulleys just have to figure out with one.

Makes sense, worn pulley bearings could create lots of drag on the system leading to more power needed to move the serpentine belt system and more fuel being used. Much cheaper to replace a few pulleys and a pair of cats.