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6670charger
10-24-2011, 05:35 AM
Is the MAF sensor the same as the O2 sensor? Found a 525i that needs a MAF sensor. Would have to travel to get the car. Doesn't look too difficult to change, but want to make sure that if I buy a part to take with me to install before the return trip, that I'm getting the correct one.

Thanks.
martyyn
10-24-2011, 04:29 PM
No,

In my rather uneducated view....a MAF sensor measures the air flow going into an engine whilst an 02 sensor sits in the exhaust measuring the amount of 02 in the exhaust gases and helps to regulate the air/petrol mix.

Im sure someone else can explain it a little better, but they are different things.
6670charger
10-25-2011, 01:53 AM
After doing some additional research, I think you're right. Seems like the MAF is under the hood somewhere near the airbox, whereas the O2 sensors are attached to the cataclysmic converter. Only question now is how difficult it is to change one out. Seems like not too bad; mostly a plug and play to a couple of hoses and the under-hood wiring harness.
Ross
10-25-2011, 09:52 AM
MAF change is a five minute job with a screwdriver and one hand behind your back.
Traveling to get? Better be sure of seller's diagnosis.
6670charger
10-26-2011, 06:23 AM
Talked to the owner via email, and it sounds like classic MAF sensor. Car idles really weird with the sensor plugged in, but, seems to run fine with the sensor disconnected.

My question now is whether the MAF in my 95 520i will work in a 90 525i, at least temporarily to drive it home, or are they completely different animals?
whiskychaser
10-26-2011, 09:20 AM
Talked to the owner via email, and it sounds like classic MAF sensor. Car idles really weird with the sensor plugged in, but, seems to run fine with the sensor disconnected.

My question now is whether the MAF in my 95 520i will work in a 90 525i, at least temporarily to drive it home, or are they completely different animals?

I dont know if the '95 520i is different from the '95 525i, but they changed the MAF types in September 1992 so you cant swap them. The older type has a wire inside. It should glow when you switch off. If you go for it, I hope its an M50NV and not an M20:D

BTW. Havent you got a 525i already?
6670charger
10-26-2011, 09:33 AM
Actually, I had to junk my 525i wagon. I'm driving a 520I wagon right now. Need to change my profile info. The main reason I'm looking at this car is because it IS a 525i. I miss the extra 50hp.

To the best of my knowledge, this should be a M50NV. I haven't seen too many Vanos engines here in Germany. The 92 525i I had was a M50NV, and I'd bet that this car is too.

Thanks for answering my question about the MAFs. I'll be looking at the car this weekend, so I plan on taking some pics of the MAF so I know what the correct one looks like when looking for one. I won't be able to pick the car up for a couple of weeks due to work schedules. My hope is to get a new MAF and take it with me when I pick the car up. That way I won't have to worry about how far or well it will run with the existing one unplugged.
whiskychaser
10-26-2011, 12:44 PM
If the engine in the new car looks like your 520i, it will be an M50. If its got plug leads it will be an M20. The M20B25 new had about 170bhp - about 22 less than the M50NV. So worth bearing in mind.
I dont know if you can tell the difference by looking at the MAFs but I think the part nos are on the top. Either way, with the last 7 of the VIN you can soon check on realeom etc