While accelerating onto the highway, (perhaps a bit aggressively, but hey, it’s a 540i, morning drivers need to wake up and get the heck out of my way, I’m late for work!!!) getting on the highway my check engine light slowly lights up and STAYS lit up…
I took it to the local BMW Auto Strasse for a check up.. The fault codes were for:

1. Misfire Cyl#8
2. Thermostat

Well, they said that the code for the misfire was “old”… How the heck is a fault code OLD?!

They replaced the thermostat and that cleared up the Check Engine light… Well, after I picked the car up, “IT” was back!!!
The light popped back on… So, I had already given them 250 for the diagnostics and thermostat swap. Needless to say, I was not a happy camper. I called Auto Strasse back and was told to change the spark plugs... "That may be the trouble..." *Not very deffinate, but that's a quote* So, that’s on the top of the list to do’s for the car.

Has anyone else had a misfire fault code? And what did you do to correct it?

The car,

1997 540i Automatic 100000 miles.
:help

100,000 miles is the number at which you need to change the spark plugs on the 99, it probably applies to yours. I would start there.

A misfire can be caused by many other things such as bad wires, a bad coil, clogged fuel injector, etc.

You may want to stop by Autozone and have the codes read again to see why it lit up this time.

It may also be your O2 sensors, not too sure. When my 7 had the "yellow light of death", my codes read that my engine was running "lean", meaning it wasn't getting enough oxygen to burn fuel. So, to fix it I got a new Mass Airflow Sensor, all new O2 sensors and got rid of my K&N filter. Since then, no problems. At 100K miles it would mean a lot of things.

Could also be a coil pack. I just replaced on in my friends moms '00 740il

Yea, to reiterate what fuddybuddy said.Autozone doesnt charge anything to do an OBDII scan on your car.Save yourself some money.The scan should tell you what is wrong, if its not an emergency just order the sensor online.Most of them are easy to replace.

Hey all,

Thanks for the inputs... I'll start with the plugs... Any fav plugs of choice? I use Bosch in my German toys... and NGK in my Jap toys... but what flavor should I use... errr.. would be the most effective for the 540i..
By the way... the light went off today.. I'm not complaining!!! WooHoo....
I'll still take it for a diagnostic check up at Autozone. Excellent advice.

Thanks again...

Dyno