hesitation in first three gears

Hey All,

I have run into a problem with my car. I have to have a smog test done on my car. I put an aftermarket 4-2-1 header on it and my buddy insisted that I wouldn't pass with the oxygen sensor mounted the way it was. I put the oxygen sensor in on the top most hole that was on the header. The header has two locations available. One at the top of the header which only reads the number one cylinder, and one back near the cv joint where the header turns into one pipe. Now the engine hesitates on take off and continues to hesitate until I get into fourth gear. The engine only acts this way when the engine is hot, not warm or cold. Can someone confirm that first my friend is right about the 02 location, and second that this sounds o2 related. The timing is perfect on this engine and the prob started after this o2 relocation.

The first (upper-most) location on the header should be pretty close to the stock location unless you did it to a CX or HF or whatever... the ones that have integrated pre-cat on the manifold.

So that wouldn't be it... not to mention that having it fuck up by moving it would require that you either put it in a spot that is too hot, or a spot that is after the cat.

first is the ces light coming on, if its the O2 senor - usually when driving between 5 to 15 miles it will suddenly run really bad for 20 to 60 seconds, then it turns on the ces and runs fine(USUALLY used very roughly)


but it could be lots of things:clogged air filter, bad or incorrect gapped plugs, brakes bind after they warm up, fuel filter, or if it a automatic the fluid level could be low(less likely) ,etc.