2002 BMW 330CI Strange Idle Problem.

[Elijah58]

Hi guys,
I am new to the forum and also a new first time BMW owner and love the car.
2002 BMW 330CI Convertible. I purchased the car about 2 months ago and am trying to get it into top shape, so far I have replaced the oil, plugs, coil packs, evap sensor, secondary fan mounts, headlights and brake pads. My issue is that it was running perfectly and upon stopping at sonic and idling for about 1 minute it started skipping very bad and SES light came on. when I was ready to leave I restarted the car and it was running perfectly and the SES light was out. I thought this was strange, then I drove it for several days with no issues and then pulled into the carwash vacuum for about 5 minutes and it did it again, I drove it a couple hundred yards with power heavily affected, I stopped, shut it off and restarted and again it was running perfectly but, the SES was still on this time. I checked the codes and it said "O2 Sensor, Bank1 sensor 1". What I don't understand is how it can start missing like it was and then restarting clears it up. Since the last episode i have driven it on the interstate at 80+mph for approximately 100 miles with no issues at all. I just don't understand how it can start and stop so quickly and be running fine. Has anyone ever encountered an issue like this?

Also on a side note: I use 92 octane with 10% ethanol and I am wondering if 87 octane non ethanol would be better?

Thanks,
Eli

[E39 Newbie]

It's possible that your upstream O2 sensor is bad, but it's not necessarily the culprit. Having said that, they are considered to be consumable items. You didn't say how many miles on the car, or if you know when the sensors were last replaced. My point is that if it's been around 100K miles since replacement then they are due.

I've found that often O2 sensor errors can be caused by a flaky MAF or by vacuum leaks. Shutting the car off, and the problem clearing after restart, is indicative of an electrical gremlin, so my first guess is MAF. But also triple-check your intake boot, the "donut" that joins the two halves (don't ask how I know this), and the "arm" that connects to the Idle Air Control Valve. These engines are extremely sensitive to unmetered air on the intake side.

But, first and foremost, as a new BMW owner, you MUST invest in a computer running either INPA, PASoft (AKA BMW Tools), or both. Or, if you have the dough, a used Autel or SnapOn scan tool. INPA and PASoft do require different cables. eBay and Amazon are your friends. A simple OBD II reader will NOT cut it.

[Elijah58]

E39 Newbie,
Thanks for the info, I will check all the things that you recommended, also I am going to start researching getting and installing the software. Would you think the 92 octane with ethanol is better than 87 octane without?

Eli

[MarcoZandrini]

The engine computer (DME in BMWspeak) adjusts fir fuel octane. But, I’d run with the higher octane fuel as the DME is tuned to handle ethanol. Just buy gas from a station that sells top tier gas. Go to www.toptiergas.com to find out which stations sell this gas.

[yjsaabman]

These cars are pretty smart. When the DME (engine computer) senses a misfire that it thinks could damage the catalytic converters it shuts down spark and fuel to that cylinder to protect the catalysts. By shutting off and restarting the engine you reset that process which is why it runs smoothly again, so I wouldn't be worried about an electrical gremlin just yet.

As was said, O2 sensor codes are more often the symptom of a running condition, either lean or rich. With these cars it's usually a lean condition. Taking a look at the fuel trims will point you in the right direction, though the codes usually will, too. High positive fuel trims indicate a lean condition where the DME is compensating for the extra air by having to add fuel. Common culprits are torn or cracked intake boots, cracked or broken crankcase ventilation lines, and split or missing vacuum caps on the back of the intake manifold.

Sent from my SM-G970U using Tapatalk

[Elijah58]

Thanks guys for the info. I work on the road and will be home in another week and will check all of these items, I will post my findings when I get back.
Eli

[Elijah58]

Ok guys, to start with let me say thanks for the info, found a intake leak and repaired and everything seems fine again. Airbag light was still on and had the airbag recall done yesterday. Light was still on, read online that anytime an airbag repair is done it must be reset. The post said remove negative battery terminal for at least 5 seconds and then reconnect. Tried this and airbag light went out but, now seatbelt light stays on, SES light on, information button on turn signal switch does not work, radio stays on after opening the door and removing the key, bright light indicator not working and heated seats not working…..WTF did I do??? Any help greatly appreciated!!
Eli

[Elijah58]

And also both taillight indicators are on.
Eli