2002 745i runs rich??

[Kessuu]

Hello from Finland,

Have to try another forum because Finnish forums doesn´t really get me anywhere...

So here´s the problem. I've a 2002 745i about 150´000 miles. For some reason it doesn´t pass the Finnish MOT. Fails in emission tests because of high CO value. The value varies between 0,4 - 1,0 (to pass, it needs to be 0,1). So it runs rich for some reason. HC- and 02 sensor values are okay. Also no fault codes. It runs nicely and also idles good. It has been looked up by local Bmw dealer and they are also little bit confused...

Changed parts: Spark plugs, MAF, air filter, few of the vacuum hoses which were cracked and fixed with tape by previous owner. I've also tried to heat up catalytic converters by driving with small gears and then straight to the smog test. Best value that I got was that 0,4.

Vacuum leak somewhere? And if so, would be much appreciated where to look for. Or do I have to just go and buy new catalytic converters??

Thanks

[Breeze1]

Hello and welcome to the forum,

What tool did you use to scan the car? Or was it scanned by the dealer?

[Kessuu]

Hello and welcome to the forum,

What tool did you use to scan the car? Or was it scanned by the dealer?

I used Inpa and dealer their own. They ran various tests. Even "bypassed" 02-sensors to test something? I haven't talked directly to mechanic and I doesn´t know the specifics

I ordered new motor temperature sensors. Just to try them out. Last emission test showed "correct" temperature of around 100 celsius. Because now i'm just guessing. And it looks like it runs rich all the time. No matter when driving or idling. It's a mystery...

[Breeze1]

I don't know why they would bypass the o2-sensors since those are critical for engine emissions. Perhaps they have a good reason for that. Best thing I can think of now is make a video showing live data from INPA on the different tabs available and post the link here.

[Kessuu]

They bypassed them just to see if they work correctly. How the values change when bypassed.

And I'll try to do video next time when i get to the dealer. I have gone through all the values fron Inpa. Everything stays on green. For me it says ok, but I'm no expert what comes to these different values...

[Breeze1]

They bypassed them just to see if they work correctly. How the values change when bypassed.

I wasn't sure when you said "to test something" but that makes sense.

And I'll try to do video next time when i get to the dealer. I have gone through all the values fron Inpa. Everything stays on green. For me it says ok, but I'm no expert what comes to these different values...

If you have INPA you could make that vid yourself. You mentioned something about ordering "new motor temperature sensors" and the temp being at 100°C last time you checked. Monitoring with INPA would allow you to check those temps (coolant and oil) before replacing them. If the engine runs too cold it will run rich...