My 95 discovery fouls out plugs and o2 sensors alot! After replacing them it runs like a champ! But after a few hundred miles it starts running like **** again. chugging at idle and the exhaust smells HORRIBLE! and Im not a fan of 8mpg! All i get for codes is 44&45 for bad o2 sensors.
Could my cats be plugged? Should i "clean them right out"?
I've gone through and replaced all my vacuum lines. New plugs and wires. An fuel pressure is good. Any help is welcome

 

Whatever is wrong upstream is what is killing your O2's not the other way around.
Start with your ignition timing, make sure it is set correctly.
Then replace your coolant temp sensor, when mine went bad it read -40*F and my ECU was flooding the engine causing bad mpg.

 

Thanks. Ill check that out

 

Changed the coolant sensor plugs and o2 sensors. Ran great except a lil surge at idle. The horrible exhaust smell was gone. But about 75 miles check engine light came back on. Code 44&45. O2 sensors. Check plugs and black like its been running at full choke!
What other sensors should i check that would caus this?Or should i just buy stock in walker o2 sensors

 

Did you also replace the plug wires and dizzy cap and rotor?
Did you use cheap wires or good ones?

 

Rplaced both. Just got orielly brand . And plugs are cheep autoleye platinum. Alota Ppl said to go with them on forums. Would one of them fancy hotter burning plugs help? Id really love to solve this because Im not a fan of 8 mpg

 

Maybe a stretch but what about your rings, might want to consider a compression test and even a leak down test if the compression test warrants it.

 

Autolite plugs are crap, I tried them and they sucked.
The plug wires you used are crap and can cause problems too, Magnecore, STI or Kingsbourne plug wires are recommend.

 

Hope i have time this weekend for a compression test. And ill get better plugs n wires.
Thanks for the info so far. Keep u fellas posted

 

There was a guy a few years ago with your exact same problem, its not a compression problem, the truck is running to rich for whatever reason.
I dont remember what his fix was.
I think it was bad fuel injectors but I dont remember for sure, sorry.