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Discussion Starter · #1 ·
Tried searching, but of course that is broken....

Anyways, i have a 97TT 6spd, 71k miles. Stock except for downpipe, HKS Super Drager, HKS SSQV BOV, K&N Drop In air filter. It has been running fine as modded for over a year.

Lately though, it sometimes runs perfect. At other times it idles like i have 272 cams and a lightened flywheel. Also, it sort of stumbles in the mid RPM range (2000-3000RPM) when cruising. Such as in first gear in a parking lot, it will just stumble until i get past about 3000RPM, then it feels like the turbo kicks in all at once. This is well before the second turbo comes on line or is pre-spooling. If i start off accelerating hard it will accelerate just fine. First turbo boosts great, then the second turbo also boosts great. Oh yeah, i also get crappy gas mileage lately.

Here is what i have tried so far. 1. fuel injection cleaner (about half a tank so far with that in it). 2. New plugs (put new stockers in, no change in how it runs). 3. Took the intercooler pipe off the throttle body to check for any major amounts of crap or sludge in the throttle body, it is very clean.

It might be throwing a code, but i wouldnt know because the check engine light is on, since i dont have an O2 fooler. I guess i could take it to autozone to check for any codes other than the O2 sensor.

Any clues? Need more info? Could it be the coil packs or the ignitor?
 

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Discussion Starter · #2 ·
Update: i went to autozone and had them read the MIL codes. There were two codes in there. One was the O2 sensor and the other was the catalytic convertor. I assume those both directly relate to my having a downpipe on the car with no cats. Does that sound right? Or could there be something wrong with my O2 sensor?
 

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Alpine Hardtopper
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Yes, on an OBDII you'll definitely get a code for catalytic converter if they're removed. But I'm not so sure about the code for the O2 sensor. Did they say if it was the front or rear O2 sensor? If your sensor is going out, often it will give really poor idle problems. If the sensor is incorrectly telling the ECU that you're running too rich, the ECU will lean the mixture out. Or likewise if the sensor is reporting that it's lean, the ECU will richen things up. What would be really handy would be to have a laptop/PDA interface for your scan port. If you have this, you can read what the short term and long term fuel trim is doing, as well as the signal from the O2 sensors going in to the ECU. This would be something like the "Auto Tap" scanner.

If it does it consistently you may be able to have your local Toyota dealer plug in to it and look for trouble. If I had to guess I would say you're probably getting a false reading off your O2 sensor, and once you get the engine speed/load up the sensor warms up enough to function correctly.
 

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Discussion Starter · #4 ·
I went back to autozone and had them scan it again. This time i could see that it is indeed the first sensor that is giving the code. Some code about slow response or something. The second I suppose is working properly by reporting that the cat is not functioning.

I guess i will search for a used one or get one from Toyota.

Thanks for your help!
 
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