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Discussion Starter · #1 ·
'99 Camry, v6, ~120k mi, College student (ie frugal :cool:, mostly bikes around now)

First symptoms: Pulsating (lightly slipping clutch feel) at certain in 4th gear when low rpm.
Current: Same pulsating whenever at certain throttle point (park/neutral or any gear). Startup is bogged, then Rough/missing idle. When started cold, continues to upshift late (even past open/closed loop changeover); if engine restarted after full warmup, shifts normal (retains some rough running).

In post-possible-fix test drives, following have shown up a few times each (in random other than misfires appearing all at same time).
Flash MIL light 3x now (twice after ~1 min warmup, once under accel uphill in test)
p0120 TPS circuit malfunction
p0302 Misfire #2
p0304 Misfire #4
p0306 Misfire #6
p0171 Lean/too much oxygen #1 bank
P1153 A/F Sensor Circuit Response Malfunction (Bank #1 Sensor #2)
So far -
On all below, checked input/supply voltage, all OK

  • MAF: checked, resistance possibly ~.5kOhm off (low), but response correct; cleaned, no change; duct is snug to manifold
  • Throttle body: cleaned
  • Acoustic flow vacuum controlled thingus on intake manifold: OK
  • TPS: checked with multimeter, scan tool, best of knowledge OK
  • PCV: was a bit sticky, replaced
  • Sparks: checked cables OK, replaced plugs NGK ***Front bank running quite rich (carbon black plugs), rear bank good (possibly every so slightly lean, light grey) - yes plugs were and are correct
  • A/F - 02 sensors:
    • Front (Bank#2Sensor#1) - heater @ 0.8 to 1.0 Ohm
    • Rear (#1#1) - heater @ 0.8 to 1.0 ohm
    • Cat (#1#2) - have not fished under seat/console yet
  • Fuel inject/rail equip: visual inspect OK, connectors snug - some acorns around rails though...
#1/Rear bank #1 sensor Manifold A/F-O2 replaced ~8k ago, OEM part, dealer install, w/timing belt change as well - problem began appearing after this.

Here is my confusion: Getting misfires on #2 bank, running rich/missing as per spark plug appearence on #2 bank - would lead to lean condition on an O2 sensor if missing - yet so far has shown lean on #1 A/F and the post-cat O2. RPM dropping, rough engine at ~1/4 throttle could be TPS...but doesn't float with the whole Rich front bank.

Current thoughts lead me to try replacing #2,#1 A/F (front), then if no-go the (#1,#2) O2 (post-cat)...looking for any other suggestions - PCM?
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