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Discussion Starter #1
Hello all, I am becoming a bit frustrated in my truck recently. It is a 1998 dodge ram 1500 sport 5.9l auto, and I'm only pulling in around 5 to 6 mpg. Granted I only drive in town, but I would at least expect 10-11 mpg. Here's some more background. About 4 months ago I added a gibson super truck exhaust, cat back set up. After about a month, the catalytic converter plugged up. In a pinch for money, I punched it out and I've been driving it. To me, it seems to be running incredibly rich, you can smell it easy. I'm guessing the reason the catalytic converter plugged up was due to it running rich in the first place. Any guesses on why it would be running so rich? I'm sick of using 1/4 tank everyday around town. Thanks in advance for any help!! :4-dontknow:
 

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Jeezus Cappy, that's a bit excessive! I'd try to get it scanned for codes. You probably have a $40 sensor ginked. Could be an O2 sensor, Intake air temp sensor, Cam or crank sensor, EGR or some other do hickey. Autozone and even up here Walmart will scan for codes. Probably your cat is plugged too. I have a guy that removed my cats, made me custom cutouts and puts a sticker on. You should be getting way better. PM me if you can't figure it out.
 

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Discussion Starter #3
Yeah it is terrible! Cat has been gutted though, so it's not plugged (That's why I gutted it), and both O2 sensors are new as of a few months, and not cheap ones either. As far as codes, I have pulled them and I got nothing other than the O2 sensors when they were bad, and a misfire on cylinder 6. Which I think was due to the O2 sensors starving the engine of gas (reading to rich).
 

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If you gut the catty on a 360 you need to move the downstream O2 sensor further down the exhaust pipe or tune fornit. According to many forums the downstream O2 sensor senses heat and with the catty gutted the flow is more free and gets that O2 sensor hotter. If the thought that it senses heat is incorrect then it is likely because the extra heat damaged the O2 sensor. In which case it may be necessary to put the sensor further down the line and tune for it. 360s average between 9-15 depending on driving style. (Ironically the ram 2500s with the 360 often get better mpg than 1500s with a 360)
 

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What plugs are you using and how many miles on them? You should only use copper plugs. You said you used expensive O2 sensors, what brand? You should only be using NTK/NGK. Have you cleaned your throttle body? They need periodic cleaning. You could use an O2 extender. Also check the back passenger side of the inside of your intake. If you see oily residue in there you need to do a kegger rebuild as then you have a vaccum leak in the intake which causes poor mileage and oil consumption. Hugh's make a kit for this. A good tuner will also help a little. Good luck.
 

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Discussion Starter #8 (Edited)
Sadly I have sold the truck. I believe gutting the cat created a whole load of issues, although as StevenBC stated, it could have been worked with and fixed. But at the time I just couldn't afford it and sold it. Now a year later and also 3 trucks later, I am back in a 98 Ram 1500 :p This time it is 5.2L though. This truck is bone stock, bought it off the original owner, an old guy I must add. He took immaculate care of the truck and when I got it I was averaging 16 mpg, which made me very happy! That was until a month ago. I am now getting 130 miles to a tank if I am lucky, and that's with a 26 gallon tank... 130/26 = is 5 MPG. I have tested for vacuum leaks and checked it with a scan tool and nothing really seems out of place. If anything vacuum seems a little on the lower end, but nothing out of spec. It is driving me absolutely mental, and I might just sell it if it keeps it up. I travel to from Maine to Rhode Island about once a month and it gets expensive. Any ideas on my new yet seemingly familiar issue? :p
 

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Clean the throttle body and well it's off check for oil residue in the back passenger side inside the intake. If you see it there it is time to do the intake rebuild. Change your plugs to the standard Champion copper plus and run a can of Seafoam in your gas tank for starters.
 

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Two things to try- Put a 16d nail through a 2x4 strapped to the go pedal and drive barefoot.
-or- tape an egg to the go pedal. (These are not my ideas, I read HotRod CarToons in the 70's)
Either path WILL lead to improved mileage.
Seriously, starting with 16mpg and then tanking sounds like driving habits.
 

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Discussion Starter #11
No change in driving habits, I try to keep the truck under 2000 rpms at all times (unless I really need to get up to speed for the highway, the 5.2 is a slug). The only change was in outside temperature. It's been around 20 degrees on average here.
 

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Winter blend has an effect on mileage but not drastic of a change. Checked for fuel leaks? Is somebody stealing your fuel?
 

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Start with plugs rotor and cap. Use OEM style copper plugs. Also clean the throttle body and run a can of Seafoam in your tank.
 

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I was getting 16.9 on flat roads,,,with the auttermatic. Now with a NV 4500,,,I hope to see it go up ever so slightly. That is if I kood just keep my foot out of it,,,That cold air intake just sounds ,,,nice. I'm not even gonna mention the Cherrybomb Vortex up under there,,,
 

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years ago, I bought a 1992 Ranger "to get better mileage" . Well I was getting only 14 mpg with the 4.0 v6. I did some research and found the fuel pressure regulator was bad. I replaced it and then got 26 mpg. Until I lifted it and put 31" tires on it. ( Still got 19 hwy)
 
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