I have 97 Plymouth Neon with 132K miles (2.0L SOHC). My check engine light keep coming on with trouble code 51, which means the engine is running lean. However, my fuel mileage is about 2/3 of normal. I can find no vacuum leaks and repair shop replaced my Manifold Absolute Pressure (MAP) sensor. When this didn't work, they said I needed new ECU/computer. I got used one from salvage, after about 25 miles, check engine light & code 51 show up again.
Just prior to this code 51, I had gotten code indicating my O2 Sensor was bad, so I have just replaced both upstream/downstream sensors with Bosch from Autozone. After just a day or two, the check engine light came on again with the running lean code. So, now, I'm wondering if the O2 sensors being non-OEM, I'm getting bad O2 readings. Repair shop had told me when they replaced MAP sensor that O2 sensors were reading OK. Just seems like all this started when I put in the new O2 sensors. I'm thinking of just unplugging them, I think the engine performance would be better than it is right now.
Any suggestions of other things to check? Things like fuel injectors, or Mass Airflow sensors would have seemingly come up before the bad O2 sensors.
Any help is surely appreciated.
Sunday, June 3rd, 2007 AT 6:25 PM