What does this code mean on my 1991 volvo 240
Heated Oxygen sesnor(lean mixture/part throttle) 94-up. (231)

 

Please keep in mind I am far from an expert.

But I had the 2-3-1 code on my 1993 240 and it was the oxygen sensor, replaced it, no more code.

 

I had previously replaced it and the sensor that i had was brand new. Do you know if it is possible that it is an ignition problem?

 

I don't think ignition, that code has to do with the "lamda" I believe, fuel/air mix.

I got my 240 at an auction and it sat for a year before I go it, I got that 2-3-1 and couple others. Check for vacuum leaks (that was my other problem, besides a fuel pump).

 

that error can be a lot of things, including air leaks in the intake plumbing, flakey or marginal MAF (or dirty connections on the MAF), tired O2 sensor, vacuum leaks, funky ECT thats making the car think the engine is at the wrong temperature, etc. if you clear the error, does it come right back?

 

I have not tried to clear it yet but your right that it is a good thing to check first.
Thanks for the input

 

Also, an exhaust leak at the manifold will cause a lean code. Air is sucked in at the leak and when it passes by the O2, tricks the O2 into thinking it's lean. It will then report to the ecu and the ecu will richen the mixture more than ideal. Running rich will kill both your mileage as well as your catalytic converter. If the code doesn't come back, then it was just a tired O2.

 

I reset the check engine light and it came right back on so that rules out the O2 sensor and i just got it inspected 2 weeks ago so i don't think that it is a manifold leak (correct me if i am wrong because i am new to car mechanics), but i have yet to check for a vacuum leak.