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Discussion Starter #1
Hi guys I have a 98 dodge ram 1500 5.2L V8 318ci and i'm getting getting on average 7 mpg I realize its a truck and it wont get great gas mileage but this isn't right i haven't done any engine upgrades other than an off brand of K&N but that's it no chip anything it is lifted 2.5 in and it has 33 in tires but that shouldn't make me get any where near 7 mpg and I also had to hollow out my catalytic converter because it the stuff inside broke and made it have no power but that shouldn't make me get 7 mpg either please anything will be appreciated Thank you in advanced
 

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Check engine light on? What codes? What is the condition of the secondary ignition? Have the O2 sensors been replaced? Do you have something in place to fool the PCM into thinking the converter is still in place and operating correctly? Is your speedo calibrated for the larger tires? Are you using any oil between changes that can't be explained by a leak?
 

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I feel you man, I got pretty much the same truck 98 club cab with the 5.2 and get around 7-8 last time I checked. Im running 35s on a 5 1/2 inch lift. Im kinda stuck too cuz idk how everyone else is getting numbers above 12. But yeah I heard about maybe going up with the rear axle ratio (idk how this would actually help mileage but it puts less load on the engine I guess) I got 3.92 gears with 35s so thats probably an issue. With the 33s id imagine you can scrape by with 3.92 gears, but if you have 3.55 id say look into it some more. Im gonna think about going to 4.10 gears if I can. Also I've heard about replacing throttle body sensors (MAP IAC and such) that might be screwing with something.
I also had a Cat issue a while back and figured that could be contributing to it but once replaced i didn't see any better mpgs.

Also, how does it run usually, does it lug down pretty easily and won't even roll forward without giving it any gas

Good luck Man lemme know if you find anything

PS nice name lol I named my truck big blue too haha
 

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No check engine light on itll come on occasionally if i put my foot to the floor and the codes then would be miss fire cylinder 1 3 5 i believe i cant remember it hasn't happened lately. What is the secondary ignition? the O2 sensors have been replaced both of them. and no Fooler for tricking PCM but there is nothing in my converter cause its hollowed out so i can drive it. The speedo is off by 5MPH and yes i am using oil between changes without any leaks
 

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The secondary ignition is the cap, rotor, wires, and plugs. Without the cat in place and nothing fooling the PCM into thinking it's there, the PCM could be struggling with the fuel calculations. Has the intake plenum pan gasket ever been replaced?
 

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Discussion Starter #6
The secondary ignition is new and the cat is in place so the sensors are there still but theres nothing in it and no the plenum intake gasket hasn't been replaced
 

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The easiest way is to look down the throttle body. An oily intake likely has a blown plenum pan gasket. The most accurate way is with a Vacuum gauge hooked to the PCV system. I don't have the link handy, but the procedure is in the knowledge base.
 

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Ok thanks come Monday ill take it into my shop and ill check it out and if thats whats wrong or isn't wrongoill let you know
 

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anymore INFO about the speedo being off by 5 MPH? Mine is like that too. Rebuilt tranny at 213K, got 235K. running the larger OPTION tires, 3.55 diff LSD new when tranny rebuilt. Still off by 5 MPH, shop said its a PCM flashing issue to correct speedo calibration. Anyone???
 
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