O2 sensor electronics testing - PeachParts Mercedes-Benz Forum

emerydc8 · #1 10-18-2007, 12:42 AM

Thanks to all. I hope I have the hot-wire type, but I guess I'll find out soon. The rubber hose on the purge valve has hardened (just like every other hose in my engine compartment that was once flexible), so I'm expecting to break it when I take it off for testing the Lambda.

Jim, I was reading your Menu 4(a) on MAF Contamination and Lambda under the headnote Fixing The Problem. Am I reading this correctly--that if Lambda is high (above 65%), you can disconnect the MAF at the canon plug and if that causes Lambda to drop to 50% then there is likely contamination on the MAF?

JimF · #2 10-18-2007, 12:57 AM

emerydc8, please re-read post#19 and #20 . . . .

In Victor's post, it appears as though his is running lean but I think yours is running rich. So I "hope" that it should drop to around 50% but may not. I guess that remains to be seen. If it does, then the DI pre-coding is working as it should.

I thought you cleaned the MAF?? If so, maybe it's really 'broke'??? Then what to do next . . . ??

emerydc8 · #3 10-18-2007, 06:10 AM

Thanks, Jim. It's always passed through emissions okay. I just thought I would take the opportunity to learn something about duty cycles and Lambda, so I jumped into this string. (I hope Victor doesn't think I hijacked it.) I'll probably end up breaking something that didn't need fixed to begin with, but at least I'll learn about MAFs and duty cycles. I've never cleaned my MAF. I talked to a friend that said he cleaned his (hot-wire) on a Chevrolet. He said he actually wiped down the wire, but I'm not sure I want to go that far. Maybe regulated air to blow it off would be the safer way.

JimF · #4 10-18-2007, 10:26 AM

Quote:

Originally Posted by emerydc8

I've never cleaned my MAF. I talked to a friend that said he cleaned his (hot-wire) . . . actually wiped down the wire

Ok, since it's never been cleaned, suggest that you do that; remove it, get some CRC MAF cleaner, spray it thoroughly, and if you have shop-air use it, backing way off from the MAF unit to blow dry. If you don't, just let it dry . . .won't take long.

Do NOT try to touch-it or use a brush for the H/W (LH) version, you could break it. It's just a very thin wire suspended inside the center.

I'll bet it will change its response for the better . . .