Help!! Car stalls often

[bimmer525]

Hi, I just got done with my 150K service on 95 525i.

I have this problem, the CEL comes on and off very often throwing the same code 1221 (O2 sensor). Whenever the light is OFF and I am rolling to a stop (at a light or stop sign), the car stalls.The RPM oscillates between (0 and 2K) when I going to stop and then the car stalls.

I just replaced the O2 sensor on my car by a dealer few months ago, but the light was on and the guy said something was wrong with the computer, but it should not affect the way the car ran. Now, I am little worried everytime I drive and this is the only car I have.

Could you please help me with the problem? What could be causing it?

Thanks in advance.

O2 change at John Holtz (Rochester)
150K service by Eksten's autoworks (Rochester)

[Black 535i]

...I had this happen to me a few weeks ago when the engine died for no reason at all. Minutes later it would be fine and then soon after die again. Turned out it was the camshaft position sensor. There are two of them on the car (mine is a 1992 535i) and one was bad. This could be your solution. Let me know. It is about a $90.00 part.

Hi, I just got done with my 150K service on 95 525i.

I have this problem, the CEL comes on and off very often throwing the same code 1221 (O2 sensor). Whenever the light is OFF and I am rolling to a stop (at a light or stop sign), the car stalls.The RPM oscillates between (0 and 2K) when I going to stop and then the car stalls.

I just replaced the O2 sensor on my car by a dealer few months ago, but the light was on and the guy said something was wrong with the computer, but it should not affect the way the car ran. Now, I am little worried everytime I drive and this is the only car I have.

Could you please help me with the problem? What could be causing it?

Thanks in advance.

O2 change at John Holtz (Rochester)
150K service by Eksten's autoworks (Rochester)

[632 Regal]

start troubleshooting by rebooting the computer first.

[bimmer525]

start troubleshooting by rebooting the computer first.

how do I do that? Is rebooting different from reseting the codes?
I have had the codes reset a few times before, but the CEL start going on and off after I drive a mile or 2.

Thanks

[632 Regal]

disconnect the battery cables and cross them for about 20 minutes.

[SRR2]

I think you should be careful how you phrase that. "Cross" isn't a generally accepted term in the electrical/electronic world, and could be interpreted by someone who's a real neophyte to mean that you "cross" the + and - connections, IOW, connect them to the battery backwards.

In point of fact, simply disconnecting the negative battery terminal and turning the key to position II for 20 minutes gets the job done. There's no need to connect the + to the - lead.

[bimmer525]

I think you should be careful how you phrase that. "Cross" isn't a generally accepted term in the electrical/electronic world, and could be interpreted by someone who's a real neophyte to mean that you "cross" the + and - connections, IOW, connect them to the battery backwards.

In point of fact, simply disconnecting the negative battery terminal and turning the key to position II for 20 minutes gets the job done. There's no need to connect the + to the - lead.

So, I assume you are saying that instead of swapping the ends to which the wires connect, I simply remove the negative terminal and move the key to position II.

[bimmer525]

Could it be as the Dealer says that the computer is behaving erratically because of some voltage surge?
I had the alternator replaced almost 8 months ago. Dealer says I might have burnt something on the computer.

How do I know if it is simply the case of the battery dying?

Just in case?
How much would replacing the computer cost?

Thanks in adavance

[George Davis]

It could be a failing Idle Speed Controller. The rpms occassionally fluctuate on my car when I come to a stop, with an auto transmission that's a pretty weird feeling, too. I suspect the ISC because most of the time it runs and idles fine. I've had some luck just cleaning an ISC, but haven't tried it yet on the bimmer. Trouble is the ISC is inconveniently located under the intake manifold.

Don't replace the computer until you're sure it's the problem. Most engine management problems are NOT the computer, it's usually a bad sensor, bad connection, or failed component.

I don't really know how to dianose a bad ISC, maybe someone else here does?

Good luck

[bimmer525]

It could be a failing Idle Speed Controller. The rpms occassionally fluctuate on my car when I come to a stop, with an auto transmission that's a pretty weird feeling, too. I suspect the ISC because most of the time it runs and idles fine. I've had some luck just cleaning an ISC, but haven't tried it yet on the bimmer. Trouble is the ISC is inconveniently located under the intake manifold.

Don't replace the computer until you're sure it's the problem. Most engine management problems are NOT the computer, it's usually a bad sensor, bad connection, or failed component.

I don't really know how to dianose a bad ISC, maybe someone else here does?

Good luck

Thanks, for your input. My gut feeling is that the computer is not at fault. I will ask Eksten's if they can check if any of these is the cause of the fault.