745i catalytic converters - United Bimmer Community

**art s** · 10-14-2006, 12:21 PM

2004 745i new in june 2004- now have 135000 miles. have been getting the "service engine soon" notice, and the dealer read the codes- bad catalytic converters. the cost is about $4800, but the price will be lower as BMW north america will participate. the question is, should the cats burn out at 130000 mi? I always used 93octane, got all service on time at dealer, oil chs q 6000 mi, etc. could the sensors just be bad? how to check? is there a secret warranty on these things? could it be a result of bad seal on that engine air injector that was thesubject of a recall? I planned to keep the vehicle for 10 years, but would hate to plan $4800 every two years for cats.

**art s** · 10-14-2006, 12:42 PM

shoot- i had 340000 nmles on my pontiac bonneville in 5years, and never needed a cat swap

**RSF5** · 10-14-2006, 12:51 PM

Well had the car been acting any differently? If the cats are clogged then it should affect performance.
edit: have you been loosing gas mileage also?

**art s** · 10-14-2006, 02:30 PM

average 23.5 mpg- unchanged since new. performance perfect.

**c1apton** · 10-14-2006, 02:50 PM

Something sounds wrong with that scenario - bad cats at 2 years old/134k? I have 152k & 13 years and still have original cat on mine.
Cats are stainless steel - did you get bad gas or try this EA80 ethynol? Sounds like something ruined them prematurely or the O2 sensors are bad - not the cats.

**TerryY** · 10-14-2006, 06:26 PM

Find someone with an infrared hand held thermometer.

If both cats are about the same temperature after running a while, then the code is wrong. Some codes are "Systemic "codes that pop up for an indirect error and cause the dealer to rub their hands together gleefully while planning the route to the bank with your money

As said before, try changing both inlet and outlet O2 sensors first. Much cheaper than cats and do a lot to correct mixture for the cats combustion.

Thinking on it a moment I think that code could be generated by the after the cat O2 sensor failing in the new multi closed loop systems.

**art s** · 10-14-2006, 06:38 PM

we never ran anything but 93 octaine gasoline. they do add 10% etoh in wisconsin at all the pumps. never tried E85, and never lent the car to anyone else. it does sound strange that the cats would be bad. i will try to check the cats with the infrared temp probes. may indeed get the dealer to try the new O2 sensors.

**xsperf** · 10-14-2006, 06:51 PM

dude, 4800 dollars for the cats, thats the biggst rip off since BMW history, i say HELL no to that, and even if they are bad take your business elsewhere!

drz · 10-15-2006, 12:38 AM

The dealership doesn't change the cat alone. They tell you that they have to put in an entire new exhaust, which drives teh price through the roof.

**art s** · 10-15-2006, 12:52 PM

well, they did say "cats", but also the 4 O2 sensors- so maybe the whole system.

stranger still, today while on theway to Sears to get an infrared thermometer, the "check engine soon" light went off. that sounds more and more like the bad sensor you talked about.

**BMWLotAttendant** · 10-16-2006, 01:52 AM

Well, if you went 135K miles in 2 years. Damn!

That's ALOT of miles. Did you buy it new? And, btw, good thing you didn't use anything other than Premium and NO Ethenol. Ethenol screws up the BMW engines.

Maybe you should consider
1) selling it and buying a 750.
We have a loaded, used 750i with 7,591 miles for $72,990.
They don't have this issue, especially with a V8 engine.
2) Forking out $4800 and seeing how long it lasts you. (I would highly suggest going nowhere else other than the dealer, because this is a dealer issue...regarding the computers/electronics/updates...etc. You are going to bite the bullet, but if anything else messes up, parts are under warranty.
3) Doing nothing. Since you have no apparent driveablity issues or gas mileage loss.

Those are my thoughts.

drz · 10-17-2006, 12:45 AM

^^ Sound advice, in my opinion.

**art s** · 10-17-2006, 05:50 AM

bought it new, with delivery in Munich. planned to go 35000 mi before I trade. stillworkingwith dealer and BMWNA.

drz · 10-18-2006, 11:39 AM

Quote:

Originally Posted by art s

bought it new, with delivery in Munich. planned to go 35000 mi before I trade. stillworkingwith dealer and BMWNA.

I just want to make sure about your mileage:

DO you have thirteen thousand five hundred miles on your car, or is it one hundred thirty-five thousand?

It would make a big difference.

**BMWLotAttendant** · 10-18-2006, 10:47 PM

Quote:

Originally Posted by drz

I just want to make sure about your mileage:

DO you have thirteen thousand five hundred miles on your car, or is it one hundred thirty-five thousand?

It would make a big difference.

No, no, no.

From my impression, he wanted to go 35,000 MORE miles on TOP of the 135,000 BEFORE he did something about the cats.

Sheesh! 135K miles in 2 years!

I'm STILL shocked about that.