Hi everyone. Ok I have a very annoying problem, but let me tell you how I got there so it'll be easier to find out what it could be. I bought a 98 mustang gt 5spdfrom auction with 83k on it. It worked fine for 5k until the motor started knocking, I replaced motor froman '00crown victoria police car with 12k miles (I know its awesome). He used my stock intake and exhaust manifold, and front pulleys. Drove it out of my mechanics driveway and the light came on. 3 days later it went off for the entire day, but the next morning it returned.Couple weeks later my cousin and I bored the MAF. I think this is when it started to accelerate a bit strange. Its mostly in the lower rpms but i woud floor it and it would shake a bit as if it wasnt getting enough of something then reach about 2 rpm and accelerate faster as it is suppose to. It doesnt accelerate like this all the time but trust me this is very annoying and i hate the loss of power. I went down to autozone and got a readout, two of them actually. Lack of HO2S Switch - Sensor indicates lean, the second code is exact same code except it says rich!! The dude at autozone told me to check the sensors on exhaust to make sure the were plugged in, we checked and they were fine. Another friend told me I might have an air leak from my intake manifold which would trigger those exact codes. I dont know what to do please help me, thank you.</P>

 

Intake leak could do that. Did you change the chip along with the motor?

 

No, I didntchange the chip with the motor, it was only the core of the motor that was replaced. If you look at the motor it looks just like my old one, the mechanic said i didnt need anew chip for it. But if I got one what kind should i get and would it really get rid of the check engine light? And where exactly could my intake be leaking??

 

By the way just recently i filled up the car with Arco 92 and the light dissappeared. I drove around and at 3/4 the light went back on, now im even more confused.</P>

 

You might want to talk to the guys in the "Check engine light - fuel tank" post. Sounds like the same problem they are having.

 

Yes, but no one has replied in that post.