i have a 1998 dodge durango and i loss engine power when i drive and while driving the engine goes loud like its driving fast but its not, and it eats up my gas super fast.
the check engine light says i need new o2 sensors but the link to the downstream sensor was melted by the catalytic converter, i want to know does a bad catalytic converter cause all this or a pcm problem

 

The computer controls your mixture and timing and all sorts of things that goes on. Without that O2 sensor the computer has no idea what the engine is doing in terms of the exhaust, and it might have tried to compensate by richening the mixture which affects both performance and fuel consumption.

Get that wiring pigtail fixed, get the O2 sensors working as they should, and then worry about the CAT if things don't get any better.

 

if the melted wire is on the post cat sensor it shouldnt have any effect on the a/f mixture, that is controlled by the pre-cat sensor, if the pre cat sensor wire is melted/shorted the computer will run off a canned tune, just like it does while it is warming up every time that you start the engine while its cold (cold engine not cold weatehr)

 

There is a reason the downstream HO2 sensor is there. It checks more than just operation of the converter as it measures CO, CO2, NOX, HC and O2. If it's sending the computer nothing, it gets confused and runs home to mama.

Get that pigatil fixed before you burn out your converter, as that repair will really hit your wallet. The reason your PCM is tossing the bad HO2 sensor code is that it's getting no signal from it, so it assumes it's bad.

When the lume is done, have that code cleared and see what happens. Also (either yourself or whoever fixes it) secure it away from the converter as the previous holder obviously failed.

 

i promise you that the post cat oxygen sensor has NO BEARING on how the engine runs, only the pre cat sensor controls that(and only once the engine warms up and kicks into closed loop), the post cat sensor ONLY measures how well the converter is functioning NOTHING MORE!!! this is standard protocol on cars and trucks.

 

Think u all I will put the sensors in then I will Probly get a new cat.

 

O yea and where can I get the link wire for the back o2 sensor because I can't install it if I can plug it in

 

Gritty, there's an easy test for the converter to know if it's working as it should. The inlet (closest to the engine) pipe will be cooler than the outlet pipe by fifteen plus degrees. If the outlet is the same temperature/cooler than the inlet then it's bad.

Use a pyrometer (digital "point and shoot" thermometer) as it'll give the best results.

The converter is just after the Y pipe coming down from the exhaust manifolds. You'll have to get up close and personal with it for the test -within ten inches to avoid interference from breezes and whatnot.