Subject: 1221 code 1995 530i, E34 Author: billjackson : member since January, 2012 : 3 posts Posted on: 2012-01-03 00:29:21

Im posting this in hopes that it will help someone else out. I will not bore everyone with all details of the crap I went trough with this 1221 CEL, primary O2 sensor, but I will say that for almost two years I have tried almost everything I could find on the web to try and solve this problem. Spraying carb cleaner around the intake, at least 10 different times, changed out both O2 sensors, cleaning MAF,cleaning ICV,changing vacum hoses,new MAF etc.
The main sympthon was that everytime the outside temp. got down to the low 50s on down to the teens the car would throw a CEL 1221 then the car would run like crap, the colder it was outside the worse it ran. What I ended up finding was that on the 11th try with the carb cleaner around the intake, and being very furstated, just spraying the crap out of everything aroung the intake the rpms finialy changed on the engine, I almost couldnt believe my ears. it turned out that my vacum leak was at the seal at the bottom of the throttle body where its almost impossibale to get at with the carb cleaner. The only thing I can figure as to why it threw the code for the primary O2 sensor was that the leak was causing cold dense air to come in and for whatever reason it was flowing down that side of the intake,and changing the air fuel mixture as it continued trough the combustion chamber, and out the exaust then onto the primary O2 sensor which was just enough to change its reading,resulting in the 1221 CEL. I also in theory believe it caused a secondary effect in that most of the rough idle, and running was because the cold air from the leak was wreaking havoc with the Air temp. sensor which is mounted driectly behind where my leak was, that in turn was making it send bad air temp. readings, to the computer and making it unable to get the air fuel mix correct, the reason I think that it corrected itself during warm weather was that the warm air is less dense and would not effect either of the sensors enough to cause any codes. I hope this information will help someone out there with the same problem, or one like it, Im not going to say that all 1221 codes will be like this, but knowing what I know now I wouldnt go buy any parts untill I knew 100% for sure that I did not have a vacum leak somewhere, even if I had to pay for a smoke test, vacum leaks are known to be a problem on the M60 engines, The other lesson Ive learned is that OEM Bosch ele. parts dont cost so much because they dont last, they cost so much because they do last.

• 1221 code 1995 530i, E34 - billjackson 2012-01-03 00:29:21 (176 views)
  • Re: 1221 code 1995 530i, E34 - Shayne 2012-01-04 00:53:10 (218 views)