Weird CEL gone after oil change???

[CAN-03runner]

1st Gen 4Runner, with 3VZE V6. It "had" a check engine light. Couldn't really tell when it triggered because it didn't start up with it on. It was either when I hit 4000ish RPM or when it would just run and idle and then randomly the CEL would come on.

2 codes, one for Oxygen sensor and one about the AC. The AC code kind of made sense since the AC has been removed and not reinstalled.

Today I finally changed the oil, and it came out like tar. Anyways, took it for a spin, CEL did not come on. I drove a good 20-30minutes. More than enough time to trigger the CEL previously and I hit 4000ish RPM.

Weird..... I've only had this truck for about 6 months and am building it up. It doesn't get driven much but everytime I drove it, CEL came on.

How could an oil change remove a CEL?

 

[ToyoTech]

pretty sure you O2 sensor is weak. i would just replace it. the fresh oil doesnt have any gas fumes in it that gets sucked back into the engine via PCV system. its been an old trick to do an oil change before smog for a better chance to pass.

 

[WoodsRunner88]

An O2 sensor wouldn't keep it from running, I had a new exhaust put on and I didn't hook up the O2 sensor for weeks and the light was on, but it never acted wierd. When I wired it in my CEL went off, and I just had to retune the timing to get my power back. I worked on a 93 honda accord once that would run ok for a few minutes, then the CEL would come on and it would just die, no matter what speed, or rpm. Found out that the distributor had some bad compnonents in it so I just replaced it and it has been running great. It's a thought.