Hello every one! long time reader, first time poster. Got a '99 Rango 5.2 slt 4x4 163000 miles. All tune up stuff is fresh, plenum not leaking ( atleast I cant see any oil in intake) new ecm, new tires. It starts, idles and runs great but, it feels weak. 5 transmission shops and 2 general repair shops all looked it over and said everything is as it should be. I have a 98 grand cherokee with the same engine and trans. and a relative of mine has an identical rango and they both have more grunt off the line and need less pedal while driving. My rango feels like its pulling a trailer all the time. Thanks for all y'alls help!

 

Have you compression tested it? Also could be O2 sensors.

 

what gear ratio is in your friends rango? and the jeep is lighter than the durango by quite a bit so that will make a different, also what gear ratio is in YOUR rango?

also dodges have a PCM not an ecm, slight difference, but still important.

 

Thanks again everyone and Ill get a pic up and stuff soon as I learn how.
Haven't done a comp test yet. How do I test the O2s if the OBD says all is good?
Oh ya I just put new calipers, rotors and pads on it and a 40 flowmaster. Sorry bout the PCM/ECM thing.
3.92 gears in both.

 

cant check the O2 sensors as far as i know

although if the O2 sensor(s) were bad your mpgs would have taken a hit

 

Have owned it 2 months when I got it it did 9-12 mpg. Correctly regaped plugs and
Put correct psi in tires it went up 2 mpg or so, just did brakes and muffler today but its seems to have improved again.

 

What kind of fuel are you using? 10% ethanol vs. no ethanol could be the difference. Don't use any fuel with ethanol in it if you can help it, these trucks weren't made for it.

 

I know you said you took it to a transmission shop, but if the engine checks out good, the first thing I would suspect is the torque converter.

 

I wish I could find gas with no ethanol in it...the only place anywhere around me are those busch card pumps...and it is 4.20 a gallon and it is 91 oct...lol But I did treat myself to a full tank of it just to see if it made a difference.

 

Also,your cat may be starting to get plugged up; it usually won’t trip a light ‘till it gets pretty bad.