Accidental Battery Discharge

I accidently got my seat belt hung up in the door when I got out of the car. The courtesy lights stayed on for many hours and pretty much drained the battery so that I could not start the car. I put a trickle charger on the battery overnight, although it never registered a full charge I was able to start the car. I ran it for about 15 minutes to make sure it was charging the battery but noticed the engine was running rough. I eventually drove the car a few miles thinking things would clear up. Came home and put the Peake tool on it and got Misfire Catalyst damaging, cyl 8 and also Cyl 7. Cleared the codes but they came right back.

This is a 98 540i with mucho miles like 235k. Any suggestions, I had previously been getting an occasional service engine soon light for a O2 sensor on bank 5-8.

Help, very frustrated old man this car is driving me nuts.

I thought the courtesy lights would turn off after 16 minutes even with no key in car?

mjalloul11,

If the belt prevented the door from closing fully, the car won't go to sleep.


golflins,

you need to find out why the cylinders are misfiring - old plugs, oil in plug well, bad coils, etc.

If your cats have more than 120k on them, they may be toast (ditto for O2 sensors). A clogged cat will cause random multiple misfires, due to back pressure.

Thanks my son had installed new spark plugs and mentioned that there was oil in the wells. I will check those cylinders tomorrow. Guess I am looking at new manifold gaskets as well.

How did the car run before the accidental discharge? Low battery voltage can cause strange electrical gremlins. Fully charge the battery, have codes read and proceed from there.

The car was running smooth although I was getting regular Peake code 20 for a sticking idle control which I had cleaned and an ocassional 23 for a pre cat sensor for bank 5-8. After I had the discharge and recharged the battery that's when I saw numerous codes about the 7 & 8 cyl misfire and that was while driving about 20 miles to my son's garage.

I had put in new plugs and rebullt all the injectors within the last 90 days. I was going to pull the coils for cyl 7 & 8 today but we got hit with 12" of snow and so shoveling took priority.

Supposed to warm up tomorrow maybe if the snow melts off the car I will pull it in the garage I hate to work on a car that is ice and snow packed then have it melt in the garage.

Love the way the car drives but these little problems have their way of pushing my buttons, I like to have a clear dashboard. I suspect I have a serious case of ADD about my cars alway have and I've own a lot of high end cars, never new, always used ones.

Originally Posted by edjack

If the belt prevented the door from closing fully, the car won't go to sleep

Ah, very good information.

Especially when debugging overnight parasitics when you WANT the car to go to sleep.

I'll add this to the existing thread on dead battery parasites:
Detailed step by step diagnostic DIY ... dead battery ... parasitic current drain