# Super weird 540i problem



## Alex540 (May 9, 2003)

My car is acting really funny. For some reason the RPM's stay at like 1200rpm sometimes in park after a long drive (30 min or more).The code is setting off any codes or check engine light or anything like that. Almost sounds like a vaccum leak, but i don't think it is. It only happens after driving and when i turn the car off and restart it, its normal again. Last night driving home on the highway in the heavy rain, my exhaust all of a sudden sounded very loud, almost similar to a exhaust leak (big one), sounded like a V8 with no cats or muffler. But that was only inside the car, outside the car, it sounded normal. Anyone have any similar problems to this?


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## Ågent99 (Jan 7, 2002)

Alex540 said:


> My car is acting really funny. For some reason the RPM's stay at like 1200rpm sometimes in park after a long drive (30 min or more).The code is setting off any codes or check engine light or anything like that. Almost sounds like a vaccum leak, but i don't think it is. It only happens after driving and when i turn the car off and restart it, its normal again. Last night driving home on the highway in the heavy rain, my exhaust all of a sudden sounded very loud, almost similar to a exhaust leak (big one), sounded like a V8 with no cats or muffler. But that was only inside the car, outside the car, it sounded normal. Anyone have any similar problems to this?


Year, mileage? Auto/Stick? Warranty in place...take it to the dealer.


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## Alex540 (May 9, 2003)

Ågent99 said:


> Year, mileage? Auto/Stick? Warranty in place...take it to the dealer.


1997 44,000 miles, auto, and no warranty in place.


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## possessed007 (May 26, 2003)

Go check it at the dealer they will diagnose the problem right away since they have the right tools. Is your check engine light on? I'm thinking vacuum leak I have one also it's a tube that is loose and always comes off I'm going to the dealer this week. check if the sound in the morning when you first start it is coming from the front passenger corner of the bumper like a whislting noise.


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## kowached (Jun 20, 2003)

*A couple things come to mind.*

The first thing that comes to mind is a failing O2 sensor. When my passenger side pre-cat sensor was failing (had not yet triggered the check engine light), I had a higher idle, and a strange drone from the exhaust that was only noticable in the cabin. I would get outside the car and listen and everything would be fine, I thought I was the only person that could hear it and was going nuts. I had noticed fuel economy falling off prior to the droning sound and was expecting an O2 sensor failure, then the check engine light came on, and confirmed that a O2 sensor was indeed failing. I changed both pre-cat sensors, and all is well. I have a write-up on how to change it at BMWtips.com

I do not think that your model year has a Secondary Air System (pumps air into the exhaust for 3 minutes upon startup), but a failure in there could create a strange exhaust note.

Finally, it might be a bad catalytic converter, which would change exhaust flow (sound), and may give the O2 sensors bad info (idle RPM).

Best of luck.


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## possessed007 (May 26, 2003)

Hmmmm....at 44000miles I doubt it the O2 sensors are finished try a fuel filter first I will also post what was the problem with my car and you can check if it's the same. 


Okay guys I have a question as well I noticed a rattle in one of the catalytics something is loose inside the cat will this affect my performance?


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## Alex540 (May 9, 2003)

possessed007 said:


> Hmmmm....at 44000miles I doubt it the O2 sensors are finished try a fuel filter first I will also post what was the problem with my car and you can check if it's the same.
> 
> Okay guys I have a question as well I noticed a rattle in one of the catalytics something is loose inside the cat will this affect my performance?


I've read that the rattling in the cat is a sign of the catalytic converter will need changing very soon.


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## possessed007 (May 26, 2003)

Alex540 said:


> I've read that the rattling in the cat is a sign of the catalytic converter will need changing very soon.


I know but you can't change just one cat you have to change the whole assembly this sucks cause it's probably 1000.00$+ I think I will have to go strip.


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## kowached (Jun 20, 2003)

Yes 44k miles is early for an O2 sensor to fail, but I know of many that have failed at 60k miles, and these particular O2 sensors are about 7 years old, and may just have had it depending on how and how often the car was driven. A Check Engine light and an error code will eventually tell the whole story.

Possessed, a rattling CAT means that the ceramic brick (honeycomb) inside the CAT is loose. This WILL eventually break the CAT up into little pieces. If the brick is breaking up at the entrance to the CAT, the pieces will block the exhaust flow, as mine did, and possible cause a "General Misfire" DTC, and a Check Engine light. If the CAT is breaking up at the rear, it will litter the rear portion of your exhaust system with "chucks of ceramic" stuck in the resonator and/or muffler. BMW CATs are covered under an 8year/80kmile federal warranty, if you are beyond that, look below.

Optional aftermarket CATs:
Carsound makes Magnaflow, they are the same thing.

Carsound 53005 2.25" in/out, round body, no air, $65: http://www.exhaustproslinc.com/carrounbodun.html

Or you could pay more for the identical converter with a polished case, 54305: http://www.exhaustproslinc.com/magpolstains1.html

If you don't know a local exhaust guy: http://www.magnaflow.com/03dealer.htm

So here are your choices:
--- $600/side for BMW Cats + installation.
--- $65/side for Carsounds + $100-$150 for installation.


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## possessed007 (May 26, 2003)

Okay My car is a 2000 model but is it standard 8 years/kms or you have to buy it when you buy the car new?


If I put the magnaflow cats. will it affect my sensor reading?


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## kowached (Jun 20, 2003)

I'm not sure how the emissions warranty works in Canada, but it is free of charge and mandated by the Federal Govt in the USA. It should be mentioned in an additional insert with your owners manuals.

I have been running the Carsounds for a couple months with no problems, and know another 540 that has been running them for 2 years, neither of us have experienced any problems.


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## Alex540 (May 9, 2003)

kowached said:


> I'm not sure how the emissions warranty works in Canada, but it is free of charge and mandated by the Federal Govt in the USA. It should be mentioned in an additional insert with your owners manuals.
> 
> I have been running the Carsounds for a couple months with no problems, and know another 540 that has been running them for 2 years, neither of us have experienced any problems.


I think i'm gonna charge the 02 sensors in my car before i change the cats, i'm still considering sell the 540i for a 04 330ci 6sp.


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## kowached (Jun 20, 2003)

*If you can get them cheap.*

I don't know if I'd change the O2 sensors without seeing the error code confirming it, but if you do, below is some info on a cheap parts source from a different forum:

"After several vendors online said they had the front O2 sensor (Bosch 13559) for the 540, then 1-2 weeks later cancelled my orders because "their supplier was no longer stocking them"....

I ordered and received them from PartsAmerica.com for $64 each plus shipping. Just FYI, that's all, since I posted that Autozone was not able to get them for me last week.

DaveInIndy
Dave In Indy"

Good luck
Dave


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