I am stumped to figure out this issue I had with my 2006 Hyundai Tucson with Automatic Transmission and i4 engine.
So I am experiencing some feel of power loss, however I got the car not too many months ago and had to do a transmission rebuild. So currently I'm not getting any codes but I noticed when I carry my family (wife, 2 infants) it lacks power to climb steep hills.
I did the digital laser temperature check on my first cat and the upstream was registering around 350 F and my downstream was about 425 F when running the engine at 2.5k rpm, than I scanned my second cat which is under the car and it was registering ~345-350 on both ends, like it wasn't having a catalyst reaction. Am I looking in to the wrong thing here, or do I have an issue with the 2nd cat?
The 2nd cat appears to be bolt on only but the bolts are completely rusted up otherwise it may have been an easy thing to take down and look through it.
The way my exhaust is designed it starts with a 4-2-1 exhaust manifold, and the 1st cat is welded onto it, than there's the L bend, a flex pipe, and a straight pipe to the 2nd cat, than it goes towards the muffler. My O2 sensors are located before and after the 1st cat only, the 2nd cat doesn't have any O2 sensors on it.
I'm experiencing about a 15% reduction in MPG as well.
On another note, I get this weird thud coming from under the car while I'm backing out of my drive way on a turn, where if one front wheel is on even pavement while the other wheel is on my sloped driveway there's this weird kabump sound. Maybe that's where I should be looking instead of at the cat?
Thank you all for any help you could give.