possibly bad cat converter 1998 XLT 3.0 4x4

Symptoms crept up all the sudden on long trip home from eastern Wisconsin all the back to Omaha 9-10 hours drive. was fine for the first 4 hours on 2 lane highways at 60mph. Then into Iowa going 70-72mph in 5th in the long hills in 5th giving it more gas but sometimes dropping speed 65-60 depending on how steep it has always done this since i owned it but not this bad. had windows down and reaching half-way up most hills would start feeling a ton of heat radiating up from underneath the truck blowing in, and truck would smell like hot burning metal, unburnt fuel, and little later on started to get a weird rotten smell, not like egg, but a faint sulfur-ish smell.

My first immediate thought was cat plugged or clogged or partially!!! got out and looked several times, never was glowing red hot, but might be only well it is acting up. NO CEL at all!

Truck has 152,000 on it now

Entire exhaust system is original, my father owned ever since it was 1 year old. he never touched it.

Exhaust does a tinny, very slight rattle too it, always has, cat heat shields are bad and have large hose clamps on them to quiet them.

I am renting a back pressure gauge on friday to confirm. Will post my findings and wether i decide to fix it, or maybe look at getting a new truck soon.

(Poor truck, I love it, but it has slowly been starting to nickel and dime me and the wife. Just spent $250 doing leaf spring shackles and hangers and shocks all the way around plus all the numerous things before that) Might as well have a payment, and a brand new slightly bigger truck and not be spending so much time in the garage, even though i do like that, but i have my fun car for that!!

No need to fool around with a back pressure gauge.

Tee in a vacuum gauge, tape it to the windshield, and drive. If you see vacuum starting to drop off during a low-load cruise, there is an exhaust restriction. It's normal for it to drop off when climbing a hill, but vacuum should hold with low to medium engine load.

You can also check the temps before and after the cat with an IR temp gun, but it's not as foolproof. Exhaust leaving the cat should be quite a bit hotter than what's coming in.

Assuming that the post cat 02 is functional, a PO42X will set as well if the cat is not functioning as well.

When was the last time the fuel filter replaced? It sounds like a dirty fuel filter under a load.

Buckeyeman said:

When was the last time the fuel filter replaced? It sounds like a dirty fuel filter under a load.

Click to expand...

I know i did it 4 years ago for sure when i moved into our house, i think i replaced it again a year ago or so again, pretty sure i did, maybe i wrote the date on the filter, will check. Thanks for the tip.

**Checked under there tonight fuel filter looks old and had some surface rust, did not see a date i wrote on the outside of it?**

**Also did drive around tonight and was getting tons of radiant heat from under the truck up through the open side windows and felt an alarming amount of heat through the floor board / firewall area only when i am accelerating decently both in town driving and interstate, no sulfur smell today, did have a little burnt metal smell! Banged the both cats with a rubber mallet no weird noise like broken insides, banged the muffler to was quiet. The front cat looks like the surface rust is starting to burnt clean off, little clean silver spots on bottom**

OH my gas mileage is about same as always right now 300-330 miles per tank all highway = 20 mpg, 200-240 miles per tank all city = 13.5 mpg.

Ok found the problem and a the solution is straight forward and easy!!!

Problem was the tail pipe tip rear section was rotated and shoved up and the tip was shooting straight at the inner part of the right rear fender about 2 inches away acting like a wall and a restriction of the flow. exhaust gases were or must have been swirling around the entire truck bed insides and blowing back around through the rear window and side windows when open and the restriction of flow was causing the entire exhaust and headers to get extra hot, bubbled the paint a tiny tiny bit not noticeable. it rotated the whole exhaust at the spring body clamp causing the two muffler hanger arms were rusty, to break off. Walker makes a strap style muffler clamp with 2 new hangers to go back through the rubbers and keep it all in check for $29 at Oreily's, will be here on Tuesday.

What happened was wife and i stopped in Wisconsin to check on a black farm cat that had been run over on the highway and looked like it was still moving, but by the time we swung around it was dead so we moved it off the highway, we had a plastic kennel with us, and i had forgot it was behind the truck, clutch roll up the hill = back over it on accident, did not see where it hit the truck, everything looked okay did not see the exhaust had been shoved upwards etc!!! easy fix and all makes sense now, put a coat hanger on for now and rotated it down, drives good, all the heat and smell is gone!!!
Yay maybe my experience will help someone who hits a rock or pile of snow/ice too or something.

Did the fuel filter too just for maintenance, and will drive the truck for 1 more year then looking at a 4 door midsize truck if we are blessed with kiddo's by then. Looking at the Tacoma, Colorado, or GMC Canyon 4 Door, or Ranger if they bring the global version back to USA in 2018 like rumored will look at that 4 door too : )

Cheers!

Glad to hear you found the problem. Replacing the fuel filter is cheap insurance too. I replace mine every 15K, especially with all this ethanol in the gas.

Yes that is the recommended maintenance interval. One of the metal triple retainer clips inside the fuel line broke coming out luckily i was able to mend it and it clipped in the two out the three teeth. Can't wait to get that muffler strap bracket on so I don't have to worry about it anymore. Just enjoy driving it for one more year while saving up some more money for a bigger 4door truck!!