So the celica's been having some hard times lately. I used to have this every-once-in-a-while stuttering and uneven acceleration and idling problem which has now become an all the time thing. It'll happen soon after I start the car, the engine will settle at 900 or so RPM, but then stutter every couple seconds, like it was misfiring a cylinder. Acceleration would be very jerky, especially in gears 1 and 2.

The car threw a check engine light the other day, and I did the paper clip thing to test, it was code 25 and 26, which is for fuel air ratio too rich or too lean.

I've got a 1995 GT with about 120K miles on it, and as far as I believe, it's the original O2 sensor, so I'm guessing it's that.. I think I have to replace the main O2 and not the secondary, is this also called the "front" sensor? And it's got a "flange"? The strange thing is that my mileage has not changed, and is good (30mpg highway).

Here's the part I was looking at from Denso, think it'll work? I'd rather do a straight replacement than any soldering or crimping...

http://www.densoproducts.com/more_info.asp...41&pid=2279

Also, is this what I should be switching out?

the top one.

x2. The top one is also way easier to change than the bottom one [For the bottom one I would suggest using the correct tool to change it as it has very weak flats that strip easily]. Be careful with the nuts when you take it off - they've gotten incredibly hot many many times.

Augh! I replaced the primary O2 sensor and still have the acceleration problems. Any suggestions on next steps? Fuel Injectors?

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I would replace my fuel filter (If it wasn't replaced yet...) and maybe throw in some FI cleaner. I had the same problem and thats what fixed my problem but then that was just my car I can't guarantee that it'll fix yours but with the exp I have it could be alot of other things too like spark plugs, bad grounds, etc....

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Is the top one the "upstream" O2 sensor and the lower one the "downstream" O2 sensor? If not, what is the lower sensor? Are these the only 2 O2 sensors?