540i Stalled Today! - BMW Forum

mrogers · 10-29-2004, 05:47 PM

I've had my car since March, and ever since about May it has idled just a touch rough for a few seconds on startup, and it would hesitate slightly the first couple times I pushed the gas pedal until it would kind of "punch through" the rough spot and hum along smoothly at a higher RPM. Very minor, not very noticable. So I haven't given it much thought because I'm usually very busy, and I told myself that the next time I had the car to a mechanic for something I'd ask him about it.

Today I'm leaving my apartment complex, waiting to turn right onto the main road. A gap opens in traffic, and as I start to press on the accelerator the car stalls! I quickly started it again without trouble and backed up from the road. I drove it a few blocks to pick something up, then drove back. It has been running smoothly the whole time.

So my question is twofold: what could cause the initial roughness/hesitation, and could it be related to this stall today? I have no check engine light on right now, and although it has come on twice in the past it shut itself off within 24 hours. I would appreciate any ideas.

Thank you!

sp0rky · 10-30-2004, 09:58 PM

timing? do you have aftermarket engine software?

mrogers · 10-30-2004, 10:14 PM

No, I don't have aftermarket engine anything...but don't worry, it's been solved...LOL, you guys are going to love this, I'm such an idiot. The car died twice more before I figured it out.

I had disconnected the battery via the power panel connector earlier in the day to reset the car's computer (hoping it would fix my seat memory amnesia problem--it didn't). When I reconnected the terminal, I used my ratchet to tighten the nut until it felt tight, but I didn't examine it that closely. Turns out that the nut had just kind of gotten to a tight spot, and there was still a fair bit of play for the ring connector on the terminal. So occasionally as I drove, the ring would shift, temporarily breaking the connection and causing everything to die. But, because of the hesitation problem I've had for awhile, and my natural pessimism whenever something goes wrong with the car, I initially thought the two were connected and initially panicked as visions of huge repair bills danced in my head.

So the stalling isn't an issue, but I'd still like to figure out the hesitations for the first couple accelerations after a cold start. If anyone has any ideas for that, I'd appreciate it. Thanks!

WindowPro · 10-31-2004, 12:16 AM

Did I read in another thread you figured out the problem?

xsperf · 10-31-2004, 01:05 AM

if the battery is disconnected, the car should still run, what if someone has a dead battery?

mrogers · 10-31-2004, 01:06 AM

WindowPro:
No, this is the only place I posted about this problem.

xsperf:
No, the car will NOT run with a disconnected battery. You need to understand that a disconnected battery and a dead battery are two different things; the battery completes the car's electrical circuit. When the circuit broke because I left a terminal loose, that means everything from the radio to the lights to the fuel pump died because without a complete circuit the whole electrical system will go down. However, with a dead battery, it still completes that circuit, it just can't provide any power of it's own. Once a battery is dead, in simplest terms it just acts as another piece of wire. Still completes the circuit, just doesn't provide a voltage difference, i.e., no power of it's own. That's why you can jump someone's car and it will run even though the battery is dead.

Don't believe me? Go out to your car, start it up, and disconnect the battery while it is running.

Speedfreak · 11-01-2004, 10:51 AM

I had stalling when I had a bad sensor. Do you have any error lights? I had a service engine soon light.

I don't think it's wise to diconnect the battery when the car is running. There could be electrical system damage.

sp0rky · 11-01-2004, 11:02 AM

Quote:

I don't think it's wise to diconnect the battery when the car is running.

He didn't.

mrogers · 11-01-2004, 11:06 AM

Quote:

Originally posted by Speedfreak@Nov 1 2004, 09:51 AM
I had stalling when I had a bad sensor. Do you have any error lights? I had a service engine soon light.

I don't think it's wise to diconnect the battery when the car is running. There could be electrical system damage.

[snapback]222193[/snapback]

I already fixed the problem, please see my second post. I had no error lights. The problem was a loose cable to the battery. In my last post, I was merely suggesting xsperf try disconnecting his battery if he didn't believe me that it would shut down the whole car

billB · 11-06-2004, 04:34 PM

Altough I never tried it on a Bimmer; if I remember correctly disconnecting one of the terminals on the battery WHILE ENGINE IS RUNNING was a well known procedure to test the integrity of the alternator. Since a healthy alternator does generate enough current to keep the engine running without a battery. when/if the engine cuts out that how they knew of a bad alternator.

The above argument needs a REAL OLD TIMER for verification.

regards
billb