Background story... been cleaning the motor with seafoam thru the intake, 1st pass gave positive results, 2nd pass I went at it more aggressive and let the seafoam get sucked in at idle. Soak time was 15~30 minutes (I dont recall how long I waited) but as expected, smoke out the back. Drove it until it cleared, drove fine. Parked it and the next day I drove it, it had a bog at approx 2500~3200 rpms. So I figure I clogged the O2 sensor and probably partially clogged the cat. No check engine light, runs mostly fine in open loop.

Fast forward to today (will most likely get this done today)... Already pulled the O2, cleaned it with brake clean (IIRC, or Elect component cleaner), re-installed and performance was improved in closed loop. What I want to do next, and this is an experiment... is to 1st yank the O2 and soak it in ATF, then brake clean after to remove any residue left, then reinstall and give it a whirl. Worst case is I hose up the sensor... which I'm already expecting to replace anyways. Once that is done then off for a test drive. If performance is restored, great, will see how long that sensor lasts before it tosses a CE light. 2nd I plan to pull that front O2 and use the seafoam spray on the cat. Watched a guy on youtube who did this on his car with a clogged cat and a 420 code, he had success with it as did a majority of the commenters did when they tried it. Worst case is no change or the cat gets hosed further. No worries for me as I have an RMW header holding up the house water heater ready to go in.

Anyways, I have not seen anyone take this approach to the O2 sensor so I guess I will be the first. Why ATF you ask? Cause it will clean better in some cases than the brake clean will. I say this cause I recently cleaned the crankcase breather on the ram, 1st with brake clean until it came out clear, then soaked it in ATF and was shocked at how much more crap came out of it. Why clean & not replace you ask? Cause its just a brillo type of screen on the inside with an o-ring to the valve cover. Swapped the o-ring put it back in and all is good. Well why did I clean it to begin with?? Cause I watched a video on a turbo discussion and the presenter made a comment in his speech that if there is too much crank case pressure the oil drain can get slow and backed up causing it to blow oil past the seals. I had unexplained oil loss... none out the slobber tube by the block, small leak up front (not enough to cover the oil loss... which was a lot) and no blowby. Since cleaning it, zero oil loss on a motor with 455k miles on it. The last time I messed with that breather was over 200k miles ago (I dont remember when it was actually it was so long ago) so I gave the cleaning a shot. Happy I did. Saved me $90 so I can spend it on the MINI :-)

Anyways, will report back results since I have not seen anyone use ATF to clean an O2 sensor. BTW, could not find anything that indicated the O2 sensor would get ruined by it either soooo....

Edit: and oh yeah, truck performs better than ever, daily driven & managed 23.6 mpg's out of it last tank (lots of subtle aero mods and custom tuning by me). No end in sight for that motor, I put 440K miles on it so I know the history.

 

update, bog gone, performance jump right away. i am thinking i need to clear adaptations and let it relearn?

going to seafoam it again here shortly... gotta have clear exhaust before i stop...

 

seafoam (half can) done, noticeably less smoke this time, maybe 1-2 more times & then done. bog came back after seafoam, just enough to notice it. will swap front sensor when done.

also, made a wrench that allows me to get the sensor out from the top... found a offset box end wrench in the box that i dont care about, cut it with a grinder, then cut an opening for the wires and smoothed out the edges, works awesome. 5 minute swap now.

ecu reset done.

 

Nice work buddy!

 

Thanks! Will see how long it lasts after the final cleaning. The bog was 100% gone on the longer drive I took to scope it out, of course it came back after that next half can of sea foam so I'm 100% sure the bog is O2 sensor related. Still planning to clean the cat when all is done and will report back here when done. The way it ran after the cleaning though I dont expect much if anything from it.

Also I did not mention... I used the DexIII/Merc ATF, non-synthetic. The same stuff I use on the Ram to keep the fuel system clean. If there is interest on the wrench I can post a pic on request.