Slow acceleration, rough idling, #2 cyl misfiring, Happened after using seafoam Options

[Cutrara]

I recently purchased a 96 st and thought I would run seafoam through it... took it up through the brake booster line. Of course it smoked like crazy, but was still smoking a few days later with a CEL on.

Took it to autozone, code P0302 #2 cylinder misfire. the plugs looked like they had a lot of grayish yellow deposits on them, #2 was significantly worse, so i replaced all the plugs with autolite double platinum and the car still has trouble accelerating... if i take off from a light it feels like i'm in third.

i also tried disconnecting the battery and resetting the afr (pull ecu hazard and efi fuses, idle for 10 mins) and still having problems. also checked all the plug wires, they look ok... I havent yet pulled off the dizzy cap.

Could it be the O2 sensor? but it didn't throw an O2 sensor code?? I suppose I could throw in the O2 sensors from my other celica, but my parts car is a 94 st obd-i and has a 1 wire front O2 sensor and my dd is a 96 st obd-ii cali-spec and has a 2 wire front O2 sensor. so idk if this will work. Haven't looked under the cars yet to take a look at the post cat sensors... if there are any?

I'm worried about my cat too cause of the misfiring. Any ideas?

[Cutrara]

Thanks for responding galcobar,

I replaced the plugs but it is still misfiring. I took them out to take a peek:

Here is the plug in the #4 cylinder... looks fine


Here is the plug in the #2 cylinder... its blacker, probably as a result from the misfiring, not the cause


I also pulled the #2 wire of my parts car and put in on my dd, same problem. I also removed the cap and rotor and inspected them. They are like new. I didnt try to switch the wires. Should I switch #2 and #4 for this?

Usually I warm the car up before I drive it, but yesterday I just hopped in and drove it. The acceleration was all there and it was running smooth, but once the car gets warm the #2 cyl misfires... at idle, at load, whatever. I took a vid of the O2 sensor voltage, you can see it go really low or go to 0 during a misfire. Could the O2 sensor be going bad? There is no O2 sensor code... or maybe the O2 sensor is just reacting to presence of gas in the exhaust stream and the problem is being caused by something else?

http://www.youtube.com/watch?v=ey484flhgvY

Lots of after-seafoam problems are O2 sensor related... I want to be more sure before I just go throwing parts at it.