well i have no clue what is happening with my car. i cannot get any codes and the car not only misfires between 2500-3500rpm it is very slow(about 2 sec in the 1/4 mile). 19%, ported head, mth, cai, header mod, 1 ball exhaust, new o2 sensor, everything was working fine for about a month, then thins started to get worse and worse. lets here some thoughts on what should be addressed first.

cheers

 

Why was the o2 sensor replaced?

Where were the upgrades done? A shop with a good diagnostic computer can find problems that don't always throw a code... This is not your common $100 OBD-II code reader, but a $$$$ diagnostic computer...

Blindly throwing parts at a running issue can get very expensive and even more frustrating very quickly... I speak from experience, although with a different car...

 

o2 sensors start to get sluggish between 30000-50000 miles, i replaced this after head install. check the post below and it will explain what has been done so far. dealer is a 100 miles away. all work was done at my shop and the car performed flawlessy untill recently.

cheers

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