ok fellers my 96 dodge ram with a 5.2 v8 is getting about 10 mpg now. I know everyone going to say out truck arn't made for fuel economy ,but i was getting like 17 a few months ago. The thing i am going to ask about is my catalytic convrter stoped up ,cause i know that has a big effect of fuel milage. I change oil about every 2,700 miles. My spark plugs are healthy air filter is new and atf fluid gets changed. Now it runs pretty rich so i don't know if that hindering my mpg. Let me know what yall think fellers.

 

We cannot tell you if your cat is stopped up. But if your MPG went down that fast, you can prolly bet it stopped up. Have you noticed a decrease in performance?

Your best bet would be to fix the plenum, get an new catalytic converter, and a new upstream oxygen sensor.

 

yeah it kinda has seemed a little less on the performance side it don't act like it can pull my atv and used to it would act like it wasn't even pulling nothing

 

Have you done your plenum yet? Might wanna have a look at it.

 

bingo

leaky plenum will cogg up that cat and hurt the o2

 

+1... Except mine went Cat making a rattle sound, replaced it with universal highflow.. 2 weeks later check engine light for bad O2 sensor, replaced with new.. check intake before but nothing looked bad decided to tape a napkin to a long ziptie and feed it to the back of the intake plenum area and low and behold oil soaked.. Ordered hughes kit and Tune up kit from summit and fixed it up..

I never thought the truck was lacking power but even after just the cat being replaced could hear and feel the difference and with everything done the truck runs great.

 

Not trying to be a dick here, but please use a period now and then. Its very hard to read your posts when its one gigantic sentence with no real punctuation.

As others said, I'd get the converter checked out. Fix your plenum (do a search here on the forum if you haven't read about it yet, or look in the FAQ section), and after thats done, replace your O2 sensor that is in front of the converter. All of the above will help your MPGs, and any (or all) could be your problem.

 

You can check the Cat with a simple pressure gauge. Drill a small in the exhaust before and after the Cat. Next use the gauge to see if you have a high pressure indication in front of the Cat compared to the rear. ( With the truck running of course and don't burn yourself ) Make sure to plug the holes after you are done. You should be able to buy self tapping plugs at the hardware store...

 

Even easier, take it for a highway drive at night, stop and look at the cat, it'll probably be glowing red (or the pipes in front of it) if it's plugged!

 

i thinki am going to have a look at my cat. i don't think the plenum has ever been changed so i may look at that. i was actually considering doing the whole thing over. it pretty stock, but i kinda wanna buy E3 spark plugs, a cold air intake, and buy new headers, cat, and muffler. so i was just going to change everthing to see if that helps. but i am kinda broke so cheap fixes i wanna try first.