I come in search of infinite wisdom and seek answers to my problems. I have a 2.2 and I put a 2.4 intake manifold and complete 2.2 exhaust system on the car with an Airiad intake filter. Then did a Trifecta tune. My goal was to open it up and increase gas mileage. It worked great for a while went from 21/30 to 26/38 but now it has went back down to 21/30????
So I did a data log on it and it says the O2 sensor is showing lean so the ECM is making it richer to compensate. Tail pipe is black and sooty and mileage sucks. Car has 30,000 miles on it and I do not hot rod it I built it for mileage.

So my question is:
1. Do you think it is something as simple as changing the O2 sensors?

2. Is there anything that can be done to make the sensor read richer? Can they be modified?

I am tempeted to put the stock tune back on it and take it to dealership but I really do not like to mess with them. I have no problem spending the money and changing the sensors out myself IF it will fix it.

One thing that may have something to do with it and I am not sure is the old exhaust system had two small convertors and the 2.4 had one larger one. I had to add a bung hole for one of the sensors but put it in the same location and everything worked great for about 10,000 miles.

3. Any ideas on what it is and how to fix it?

Thanks in advance.

 

Have you checked for an exhaust leak?

 

There is no exhaust leak. Does anyone have any ideas on how to fix this problem?