M3 Down!!!

Apparently the code is for the MAF but Brett says Subaru's will throw a MAF code for a bad o2?

That true? I can definately see one (or both) of the two pre cat o2's dying on me. Good thing I have 2 post cat o2's and can use those to test and see if I do indeed have a bad o2 sensor. But I'd figure I would be throwing some o2 related codes.

 

i'm curious as to the context of all this?

 

I did header install. But the MAF is on the other side of engine and was never touched or anything hence why I'm confused.

 

Here's basically what is going on.....

Okay I have some issues after a header install. I was expecting some o2 issues but it doesn't seem to be so. If you crank car up it idles just fine. But if you go to drive it, it severely limps and the SES light comes on.

I use Carsoft 6.5 to scan my codes. According to Carsoft I'm throwing HFM sensor. What in the world? The MAF? So I take it off and clean it and try again. Same thing. If I drive the car it'll run very rough and idle rough. Turn car off and the SES light is gone. Idles just fine until you drive and the cycle starts again.

Now I haven't even touched that dang sensor or the intake. Weird. Any ideas people? Does this sound like the MAF is indeed bad? How can I test it without spending a ton of money on a sensor I may not need?

 

.... ?

 

nope no wiring or curves involved.

 

And yes the 2 front o2's are in the right place....first thing I checked.

 

Dude you suck....



and

http://bennyhills.fortunecity.com/priory/30/do.wav

 

I'm thinking one of the o2's is indeed borked.

 

LOL

 

German for MAF. High Flow Meter
German for CEL. Service Engine Soon.

 

The 4 o2's are in the headers themselves on the M3. 2 precat and 2 post cat. The post cats purely monitor cat efficiency and the M3 has to drive a while to pop that CEL. I'm not using the post cat sensors but they are plugged in for the heater circuit. And the cats are in the headers too hence why I am doing a header install (catless FTW).

 

Yeah. I'll do a live data test tomorrow and see if I can see obvious incorrect voltage outputs from the o2's.

Any idea if a broke o2 will just read a constant value or what?

 

Does it have some sort of exhaust recirculation valve? I've seen one of those get stuck open due to a carbon deposite on a "2.5RS" and cause similar issues

 

No clue. It's a simple four wire o2.

 

Coolbimmer borked his car....that what happened.


Researching I found a post that the tags on the sensor don't mean jack. Just because it says 1 on the sensor doesn't mean it goes into bank 1. So I'm gonna swap the o2's around and see what happens.

 

just pull them out and beat on the ground a few times

 

Yeah.....riiiiiiiiiiggggggggggghhhhhhhhhhhtttttttttttt.

 

could it be the equivalent of going catless on a subaru and needing the little 02 sensor adapter to fool the cel?

 

In the Subaru you still run just fine with that catalyst inefficiency CEL. In my case I'm in limp mode.

Latest reports.......another M3 owner said his sensors yellow tags were 'mislabeled'. And he was running just like mine....perfect idle until you drive it. Swap his sensor and voila fixed. So I have a starting point tonight and thankfully it's only about 20 mins worth of work to swap and test.

 

did you pull the O2's before removing the manifolds?

 

You can't. Have to drop manifold and then pull o2's on stock. If the o2's were dead I should be throwing multiple o2 codes.



Note I said 'should'. I will swap o2's and see how it goes.

 

BMW DME is way smarter and advanced than the Subaru ECU.

I think I have the o2's swapped. My car has 4 o2 sensors. 2 pre cats and 2 post cats. Car is a true dual exhaust all the way to the muffler so it has sensors in each pipe. My headers are two piece just like factory. If you put bank 1 sensor (front header) in bank 2 (rear header) and likewise the other way then bank 1 is reading for bank 2 and the values aren't right in conjunction with the engine pulses. Hence limp mode.

Swapping sensors when I get home from work tonight.

 

4 O2's holy hell batman. and i was catching hell just getting the ONE out of the bike. keep us posted

 

Least you can interchange them all if you splice them. And least they are all narrow band so they $60-70 each instead of the absurd $180 the Subaru front o2 was.

 

From what Cicio and Doug have told me....the DME is vastly enhanced over the Subaru. More bits and many many many more tables. I think it takes like 45 minutes just to read and write the mapping to a format for Doug to read it and alter it.

 

lest you forget who coolrex is

 

this..

after all the germans invented the term 'ANGST'....

ETA.

i had an M3 for a while. bought new. car had me worried till the day i sold it. what worried me the most was that i wouldnt sell it before the warranty expired.

nice cars, nice interiors. but can be expensive to maintain. the germans seem to get a bit carried away with the electronics in their cars too. and sometimes they have issues.

 

M3 is alive and well dudes. I'm stoked!

 

Mercedes is a perfect example of electronics gone awry. I think half the lots were full of loaners at one time.

 

So what was it? Swapped O2s?

 

he forgot to plug them in

 

Bank 1 precat o2 was in bank 2 and vice versa. Switched them and voila.

 

good cover story

 

Cover story? Lol

 

I knew a mechanic once who's favorite line was