P0441, rattle, miscellaneous issues
I'm facing down 2-3 different problems with my '99 XJ, and need a hand in figuring out where to go from here. Forgive the novel below; I’m providing as much info as I can in the hopes that there’s something I have not considered.
The most obvious problem is that the CEL has been on for a month or so, and throwing a P0441 code. I've read a number of threads on this code; my understanding is that the PCM is detecting that vapor is not being purged properly from the charcoal canister. Note that the canister itself was replaced in 2012.
The secondary problems I’m facing are that despite the shift lever and dashboard lights indicating that I am in 2WD, the TC (NP242) feels like it’s in part-time 4HI, a wandering rough idle (and an intermittent near stall/surge at idle), and a rattling sound/vibration from the driveline.
The Long And Ugly Backstory
The problems begin around the time that I had AC repaired (new evap core, work done by a local Jeep dealership). Around the same time, I removed and cleaned out the throttle body, seafoamed the engine, replaced the TPS (trying to get rid of a 100-200 RPM wander at idle), replaced the spark plugs, wires, and distributor/rotator cap.
About a week after the AC repair, the following symptoms emerged:
(1) on one drive, the engine developed a rough idle that nearly caused a stall, with a surging engine when it wasn't stalling (~200-2k RPM).
(2) slight smell of gas in the cabin during this drive (as if it was running lean)
(3) additional codes for the front O2 sensor
(4) a hard rattling sound from either the engine or tranny; both have new mounts as of 2012 (brown dog up front, OEM for the tranny)
I cleared the codes, and they did not come back, so my assumption around (2) and (3) was an intermittently failing O2 sensor. I put it on the list to fix "soon". A few days later, it overheated in traffic with the AC running (the aux fan wasn't coming on); I had that repaired (replaced the fan, as the electrical signal was good - no signs of a lurking bad ground connection).
Code came back, and I experienced the same idle stall/surge problem again. I checked that the gas cap was tight (it was), but went ahead and replaced it with a new locking cap just in case the seal was bad. No change.
Given that this all started after having the AC work done, I brought it back to the dealership. They replaced the leak detection pump and purge solenoid, but did not diagnose/hear the rattling or figure out what had caused the idle issue (as it wasn’t happening for them).
Cleared the codes, but the light came back on a few days later despite the LDP and solenoid replacements. Brought it back, replaced the front and rear O2 sensors, and asked them to investigate. They threw up their hands in defeat.
For the transfer case, I’ve recently changed the oil (again, done by the dealership), so my suspicion is that the linkage has finally given up the ghost. Replacing with a Novak setup and adjusting within a week or so.
Any ideas what I am missing with purge issue, rattling, and wonky idle?