Check Engine Light

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07-08-2004, 01:36 PM
Unregistered

Check Engine Light

Driving home last night and felt the car start to idle rough while sitting at a stop light. Noticed the RPM dropping way below 500 then back up over 1k. Put it in neutral to rev it up a bit and once over 1k RPM, it cleared. As I let it go back to idle, I noticed the Check Engine light was on and the idle was once again rough. but eventually smoothed and the light went out.....but only for a while as it would do it again after a few minutes. Each time I would rev it up over 1k and it would again smooth out, only to come back again. Let the car sit overnight and all seemed to be fine this morning. However after about 40 minutes the problem was back and the Check Engine light was on. So as not to get stuck on the road, I pulled it into the dealer (god, I hate them) and put it in for service. Of course the whole time I was waiting for an advisor, the car idled just fine and the light never came on. Seems the problem in intermittent.

Any ideas on what coul be the cause of this?

94 530i - 201k miles
07-08-2004, 05:23 PM
winfred

the v8s are haunted with vacuum leaks from crappy intake gaskets and the pcv plate on the back of the intake (sometimes it makes the motor smoke real bad others it makes it run bad) then the over adaptable injection system goes nuts and really messes up the running, case in point, we had a 94 740i come in for a motor swap (the dealer said the motor was a bad nicasil block) it turned out to be a dieing fuel pump screwing up the running, so the dealer is not always correct (hmmm $200 fuel pump or $5500 engine job)

the catyletc converters can also clog up and cause problems
07-08-2004, 06:25 PM
Unregistered

I hear ya......I hate the damn dealers.

But they pulled Fault Codes 201 and 203 today indicating problems with the O2 sensors. See my post titled BMA Rocks for the story on how much the dealer wanted to fix this.......
07-08-2004, 09:00 PM
winfred

theres about 4 different o2 sensor codes and only one suggests that the sensor is dead

Quote:

Originally Posted by Unregistered

I hear ya......I hate the damn dealers.

But they pulled Fault Codes 201 and 203 today indicating problems with the O2 sensors. See my post titled BMA Rocks for the story on how much the dealer wanted to fix this.......
07-09-2004, 02:55 AM
chris530it

i had the same thing happen to me....

dealer told me i needed a new intake manifold...total lie.

fixed with new mass air meter. still about $375, but fixed.

chris
94 530it