I recently purchased a 2005 Trailblazer (4.2 l) with less than 80k miles from family. So I’m pretty familiar with the history. Unfortunately that history involves a misfire code last year and my dad taking it to the local guy he knew in town. He changed the spark plugs and cleared the code. It came back. So my dad took it back and the guy poured a quart of ATF in the gas tank, cleared the code again and told him to see if the code comes back. It did, of course and now it had been being driven with misfires for weeks. So I checked the code and it was a cylinder 3 misfiring. So for $60 and 10 minutes, I replaced the coil and all was well. Well, until recently when I started noticing power loss on highway inclines. Sometimes I can push it to the floor without it going any faster. Other times on incline, it just seems lacking in response/sluggish. Otherwise it seems to drive fine but I’ve also started noticing a low rumble coming from underneath the mid-rear of the vehicle. Not super loud but I’ve noticed it. No rattle but it does get louder and can be heard in the car when accelerating on the highway.
I’m limited in experience, knowledge and tools but have been tackling increasingly harder projects with my cars with success (not that any have been all that hard). I did the only test I had tools for and I’m not even sure I did i correctly but I checked inlet/oulet temp of the cat with an infrared gun. I drove the car around the block, then parked in my driveway and had my wife keep it a 3k rpms while I checked the temps. I got 500 inlet and 400 outlet. Checked it twice. From reading online, I understand this indicates a pretty obvious problem. But then why don’t I have an engine light or code? I’ve been reading and watching a ton on this the last few days and it lead me down a path towards the cat and these temps seemed to confirm a problem. Does it sound like that’s the case even without an engine light/code?
I researched the procedure for replacing the cat. It seems I have multiple options but I’m seeing some issue with each one.
I considered the lacquer thinner in the gas tank just as something cheap to try first but I’m figuring if the cat clogging is from the misfires, wouldn’t it most likely be pretty baked/welded on? I’d love to remove it and see if I could clean it by soaking but from my research, it sounds like I’d need to cut the pipe or remove the transmission crossmember to get it out. Cutting the pipe means I can’t put it back (or does it?) and removing the cross member makes me nervous, being a novice.
I see there are universal cats that say they work with my vehicle and not very expensive. I tried watching youtube videos on these installs but all the ones I could find skipped the actual installing moments. Is it really just as easy as cutting out the old cat and clamping this one in with a piece of make-up pipe?
Then there’s the direct fit. But now I’m back to the issue of needing to remove the crossmember. This will also cost about 2.5x as much as the universal instal and approaching more than I want to spend on the vehicle. If I knew it would take care of the problem and I could accomplish it, then I’d do it. But neither is guaranteed. I’m also concerned about needing to remove the 15 year old flange bolts that are way up in an awkward place so I’m nervous about breaking one.
Thanks in advance for any insight/help anyone is willing to offer. I’m pretty set on attempting something, I just haven’t decided what.