have a 323is that I have done a lot of work to, but have a couple of issues that I have not resolved yet and was hoping someone here might have some answers. When the car is cold, or has not run in about 8-10 hours, when I start the car it runs as though it is running on 2 or 3 cylinders for approximately 30 seconds. It never goes beyond the 30 seconds, and it idles at a rock solid 700 r.p.m.'s at all times afterwards. I recently had the vanos replaced at a BMW dealership, and the car did not do this prior to having the vanos replaced, although the vanos was not working at all when I took it to them. I thought maybe I had gotten some bad fuel, so I used some fuel injector cleaner and octane booster in fuel tank and then replaced the spark plugs with iridium/platinum fusion Bosch plugs. I am getting a fault code for secondary air, so I replaced the the vacum control switch and the vacum module that connects to the exhaust, although I did not think that it is the cause of the cold idle problem. It still did not fix the fault code though, after I reset the code it comes back on after a couple of days, could this be a faulty Oxygen sensor causing the fault code, or something else? And what could possibly be causing the car to have such a rough idle at start up? The car does not burn oil or smoke or make any wierd noises when running by the way, exhaust analysis shows it burns perfect, gas mileage is dead on, and power seems o.k., no vacum leaks also. So what do you think? Any ideas or thoughts? thanks for your help, Jon
I have 3 E36's and they ALL do the rough idle thing under certain conditions. If the car has been sitting for a while and then I start it to move it to the other side of the driveway and then shut it off (after it's only been running for a minute or less), the next time I start it, it will run like CRAP for about 30 seconds (like you said, like it's running on 3 cylinders). After that, the idle smooths out and it'll run perfectly from then on. They have all done it since new and I have no idea why!? It sounds like yours happens slightly different than mine but the symptoms sound identical. My guess has always been something related to fuel delivery, almost like it's starving for fuel until pressure comes up and the fuel rail fills up again. Hopefully someone can give a definitive answer. I stopped worrying about long ago because it hasn't cuased any problems in 13 years but I am still curious...
Secondary air code on e36 is usually caused by a bad secondary air pump. Expensive but easy to replace. Poor idle on startup can be caused by leaky injectors. My wife's car does this, but I have not had time to clean them.
Thanks for the response. Do you think the "Check Engine" fault would show up for secondary air pump even though it is working? Also would it show up a day or two after being reset, and also at a time when the air pump is not even running? Usually I am going down the interstate when the "Check Engine" light inadvertantly comes on. All the components associated with the air pump have been replaced with new also. Thought this could possibly be an Oxygen sensor since it shows the fault for only 2 cylinders. I will have a look at the injectors for possible problems, I thought the cold start idle problem could be fuel related and was starting on process of elimination with that part of the system. I purchased new fuel filter and was going to purchase fuel pressure regulator to try that as well, but will look at injectors first. Thanks again. Jon
Your O2 sensor cannot show a fault for only 2 cylinders. You car has 2 pairs of O2 sensors, one pair for each bank. If the code says secondary air, I have always seen that the cause was a secondary air problem. Yes, the check engine light can come on at any time for that. If the secondary air pump is bad, it will turn on the light. What is the specific code it sets? Have you tried activating the secondary air pump? Replacing O2 sensors because of an O2 code is a common mistake. Very often, the code is thrown for air leaks, exhaust leaks, bad MAF sensors, etc. I suggest you stop throwing parts at your car and try to find the real cause before you end up broke, pissed off, and staring at your lit check engine light.
