850 Fault Code 2-3-2 "long term fuel mixture too lean or rich at idle"
 

My 1995 850 Turbo with 147,000 miles just gave me a Check Engine light. I read the fault code from the diagnostic test unit with the red LED. It gave me the code 2-3-2 which is listed as " long term fuel mixture too lean or rich at idle". The same code, 2-3-2, was stored at least 5 times... there were no other codes stored.

The car mostly runs and idles normally. The idle is not as silky smooth as I wish it were, but I think I need new engine mounts to fix that. But the idle is not what I would describe as 'rough' at all. I use 93 octane unleaded gasoline.

About 3 weeks ago I did have one strange thing happen with this car. While driving on the highway it would not shift from 3rd gear to 4th gear (automatic transmission). I stopped the car then started again and this odd behavior went away. Since then I have not had any trouble with the transmission. When this happened, I did not get a check engine light. I posted this issue here: https://volvoforums.com/m_67751/mpag..._/tm.htm#70807

The only maintenance I have done on the car recently was to replace the PCV system. To change that I did have to remove the fuel rail and injectors. But I did that job 3 weeks ago and I have driven every day since then and have not had any check engine lights or problems. So I don't think that job has anything to do with this engine code, but I thought I should provide the info just in case.

I cleared the codes but have not driven the car so I don't know if the code will get set again or not. After my drive home tonight I will post whether or not the check engine light comes back on.

I did some google searches and found something about a Ford Scorpio having a defective Mass Airflow Sensor and having similar issues. According to the website, a defective MAF on the Ford Scorpio can cause engine codes for Fuel System too Rich or too Lean and it could also cause the automatic transmission to not shift from 3rd to 4th. I don't know if this data is applicable to a Volvo 850, but it sure is an interesting coincidence.
http://www.fordscorpio.co.uk/maftest.htm

I cleaned my MAF about 2 months ago with special MAF spray. I did not notice any difference in the car after cleaning it.

Does anyone have any idea as to what could cause this condition? Any suggestions on how to troubleshoot / fix the problem?

Thanks!

RE: 850 Fault Code 2-3-2 "long term fuel mixture too lean or rich at idle"
 

After driving home tonight, the Check Engine light came on again... I checked the code, it was the same one. 2-3-2 - long term fuel mixture too lean or rich at idle.

Any ideas?

RE: 850 Fault Code 2-3-2 "long term fuel mixture too lean or rich at idle"
 

Most likely caused by bad or very worn Oxygen Sensors. I assume they have not been replaced as they are $$$$$ BUT, you can purchase Generic Bosch 4 Wire Sensors and wire them in yourself. I have done this since I had a source to get the generics for FREE. They have a funky connector with little screw down "butt connectors" I found that the Generic Blue Crimp "Butt Connector" for 16-18 Guage wire from Radio Shack, Home Depot, Lowes etc. with fit inside the waterproof housing provied with the sensor perfectly! Making it a much easier install. You should always replace the sensors as a set. The ECU adjusts for the age of the sensors and replacing one will sometimes cause codes to be thrown for the older one.

BTW check for Vacuum Leaks FIRST! I would say that 50% of all CEL lights are related to vacuum leaks. The 850 Turbos have more plumbing than NYC and it is just as bad!

RE: 850 Fault Code 2-3-2 "long term fuel mixture too lean or rich at idle"
 

Thanks for the suggestion 1996850turbo. I have a feeling you are right and I need to replace both oxygen sensors.

I have proved that the Mass Air Flow sensor is not the culprit. (I have a 2nd 850 that I was able to switch MAF sensors with and I still get the same code with the known good MAF.) So I guess my next step will be the Oxygen sensors. You are right, I have never replaced them and I have 147K miles on the car.

Would you happen to have the Bosch model numbers for the front and rear O2 sensors that you used? I'd really like to use the generic Bosch ones instead of the super expensive 'direct fit' versions. I think that if I had the right model numbers I could probably find them locally.

Is there any good way to test my existing O2 sensors to verify they are indeed bad?

Thanks for your help!

RE: 850 Fault Code 2-3-2 "long term fuel mixture too lean or rich at idle"
 

I finally figured out that the code was caused by a hole in a vaccum elbow down under the intake manifold near the power steering pump.

Thanks!