Hi all,

I am having some troubles with my 2004 545i I hope you can help with! I love this car and have owned it for at least 7 years now, but it is wearing me down! I have searched the forum, but when I find a thread with similar problems, there is never a fix reported. Here is my issue...

The car has been randomly stalling when slowing down coming up to a light, or turning slowly. I would not loose any electrical, i.e. dash stayed powered and radio would still be playing. It used to always restart right away and I would keep going although it would give me all sorts of trouble codes in the engine, ABS and transmission modules (Launch x491 mini, I do not have a laptop to do ista). Not always the same codes. Lots of engine speed codes, which led to me replacing the crank position sensor, but that did not help. Lately it has been getting worse. It does not happen on the drive in the morning, it usually is worse with a lot of starts and stops, or stopping at different stores where the car is off to heat soak for 15-30 minutes. Now when it stalls, it may start but quickly stall again, or I may get a crank and no start with the relays behind the glove box going crazy clicking on and off. I turn the key off and try again and it runs perfect for may be 5 minutes, an hour, a week and then it happens again! Scary when it stall going around a corner in traffic and losing the power steering.

With all of the random codes I believe it is an electrical issue. I have checked battery connections in the trunk and under the hood. The battery may be a couple of years old but no issues with starting power or dying when left for extended periods. I did some research and replaced the IVB (can't remember the exact lettering, the fuse/relay module by the engine computer under the hood) which did have bad/cracked solder connections. The problems continues!! Last night I hooked up the Launch and recorded engine voltage while driving. Voltage stayed between 13.5 and 13.8V except at one spot where it dropped to 0V for less than a second. I never saw it when it happened and I didn't remember a stumble/stall. With the key off, it reads 12.6-12.8V.

I just don't want to keep throwing parts at this thing. I love it, but a 17 year old V8 BMW with 340,000 kms is not exactly appreciating in value! lol

I am currently thinking it may be the alternator shorting/voltage regulator on the way out. Thoughts? Any direction or advice would be greatly appreciated.

Typical list of error codes I get...

 

It could also be a vacuum leak.

 

Do a voltage test on the alternator with a voltage meter. You should see it drop while doing a test. If it does then you know where your problem is. You're going to have to be patient and run the test for a few minutes at a time until you're satisfied that it's not the alternator. Then work you way to the cables to make sure you're getting a good ground.

 

Hi, thanks for the suggestions. Unfortunately, the wifey wanted to go boating on the weekend, so not much done in the way of troubleshooting.


Donpb, I can see how a vacuum leak could cause a stall at low RPMs, but not sure how that relates to all the trouble codes I get when it does stall?

seanjordan20, I know I have to do this... just not looking forward to trying to a test lead on the back of the alternator!!

 

If anyone wants an in depth look into a 545i charging system/alternator problems with a great description of the system, check this out.

https://www.picoauto.com/library/cas...nication-error

 

When I had a vacuum leak, it resulted in lots of codes throwing because the ECU tries to compensate but eventually fails.

 

OK donpb, I'll check the fuel trims when I work on the car next. That should show me if I have a vacuum leak. Raining here a lot lately and no garage, which sucks! What did you do to fix your vacuum leak?

Thanks.

 

I had one cracked hose. Replaced it and all codes magically went away and car runs great.

I was experiencing the exact same things as you described. It was really pissing me off.

I am not saying you will have the same finding. Just check into it to see what you can see.

 

OK, so I checked my car for vacuum leaks, but found none. Checked all around with brake fluid. Once the car was warm, the long term fuel trims were almost 0 and the short trims hovered around 2.5, which is well within acceptable range. Well, nothing big enough that I believe would stall the car.

So, yesterday while it actually wasn't raining, I ran the car. I drove around my little town trying to get the car to stall while watching the voltage. Nothing. Not a glitch. I came home and sat in the yard with the engine running trying to get some heat soak. I stopped and started the car several times and watched the voltage. Nothing unusual until... the car just wouldn't start!! No crank, nothing. Everything else in the car worked, i.e. dash, radio, HVAC, etc. When I turned the key, the voltage did drop a little like it was trying to start the car, but absolutely nothing from the starter. Not even a click from the starter solenoid. I tried taking booster cables and adding a ground from the engine bay jump start lug to the engine and that did not help. I checked voltages from the engine bay positive jumper lug to the engine and had full voltage. I was getting no errors on my code reader. I checked the two green relays in the glove box and swapped them (not sure what they are for, but was trying anything lol). No change. I gave up and let the car cool down. Went out 30 minutes later and boom, the car started right up!

Can someone with better electrical knowledge than me (which isn't much) lead me to some relays and/or connectors/wires to check? In my head I believe it is a wire/relay/connection that is losing continuity when hot. I could be wrong, but I don't know which spots to check. Specific locations would be very helpful and appreciated! I don't particularly trust taking my car to anyone local although I may have to because using my old Dodge Ram with a 5.9 gasser and big tires as a daily driver is costing me a fortune!! Thanks in advance!

 

Try disconnecting the IBS.