So, it rained like heck yesterday afternoon and I ended up screwing around a little too much in it. I drove through a little less than a foot of water without issue. I shut the car off after getting back to the office and went inside - at this point the car had been running fine as usual. Less than 2 hours later I got back in the car and when I started it it had the worst "miss" I have ever experienced. Due to the amount of rain, I guessed that I had some water under a coil, but absolutely had to get home - so I drove it the 40 miles to my house, missing the whole way. Power was virtually non-existent and I struggled to keep the car up to 65mph. Pulling into my garage my car sounded like a steam locomotive - with a repetitive hiss coming from below. I pulled all the coils and found no water. I found some oil in one plug galley, but nothing major. I cleaned and reinstalled the plugs and coils without regard to locations. On the trip home I was able to pull code p0300 random misfire. After cleaning & reinstalling coils & plugs I had no code - but still a horrible miss with the repetitive hiss. I had a meeting I needed to get to and on the return trip I was able to pull a code p0305 random misfire on cylinder 5. I haven't pulled #5 again, yet. I'm basically convinced at this point that somehow the cat is plugged. I tried for over an hour to remove the upstream O2 sensor and only succeeded in rounding off its hex flats. Climbing under the car I found a "huffing" or "hissing" noise - much like a steam locomotive - blowing exhaust gasses out of a few different holes in the bottom of the muffler with some force to it. There is exhaust - without a strong particular odor but very humid - blowing out the tailpipe. At this time I'm now convinced the cat is plugged but have no easy way to test it. It's possible something has plugged the muffler (perhaps the matrix in the cat disintegrated?). Some brief internet searches hinted at "thermal shock" (heat quench) being a potential cause for instantaneous catalytic converter failure. I guess it's possible water rapidly cooled the cat and shot it in the butt - and possible had the stuffing blow further down the pipe and plugged the muffler. I'm now not sure what to do to troubleshoot and potentially fix it.
I'm looking for input. Is there a simple step I can take to rule out the cat? I'm almost ready to sawzall the pipe between the cat & muffler to rule out the muffler and then sawzall the pipe before the cat to rule out the cat if the muffler isn't the culprit. I don't ~want~ to do that if I don't have to. For background - I had some patchwork done to exhaust and some pipe was welded in to replace some rusted/holey pipe between the cat & muffler a couple years ago - unbolting is not an option. I'm also 100% sure I won't be able to unbolt the downpipe from the manifold without some serious help. ~If~ it's the cat, I'm willing to have my guy weld in a universal replacement and a new muffler - but I don't want to send it over to him until I know what's wrong.
Any thoughts?
I'm looking for input. Is there a simple step I can take to rule out the cat? I'm almost ready to sawzall the pipe between the cat & muffler to rule out the muffler and then sawzall the pipe before the cat to rule out the cat if the muffler isn't the culprit. I don't ~want~ to do that if I don't have to. For background - I had some patchwork done to exhaust and some pipe was welded in to replace some rusted/holey pipe between the cat & muffler a couple years ago - unbolting is not an option. I'm also 100% sure I won't be able to unbolt the downpipe from the manifold without some serious help. ~If~ it's the cat, I'm willing to have my guy weld in a universal replacement and a new muffler - but I don't want to send it over to him until I know what's wrong.
Any thoughts?
