O2 sensor electronics testing - Page 3 - PeachParts Mercedes-Benz Forum

JimF · #31 10-17-2007, 11:54 PM

Quote:

Originally Posted by myarmar

Inside LH MAF

I had one that I almost took apart . . . but I didn't. Tnx for the pic of the guts!

emerydc8, yes that's the device; the rubber hose slides onto a rigid metal tube. Good Luck w/ the new meter.

emerydc8 · #32 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 · #33 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 · #34 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 · #35 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 . . .

190eand me · #36 10-18-2007, 08:50 PM

I hate to tell you this Victor but a o2 sensor is nothing but a low level battery...that activates when heated......test my theory by taking it out of the car ...hook it up to your VOM meter and use a propane torch on the tip and see what happens to the voltage. interesting.

and it the only way to tell if its working or not

emerydc8 · #37 10-18-2007, 09:13 PM

Thanks again, Jim. I have the rubber connector for the MAF on order. I figure that will break when I take off the MAF. I'll post the results.

JimF · #38 10-18-2007, 10:10 PM

Quote:

Originally Posted by 190eand me

I hate to tell you this Victor but a o2 sensor is nothing but a low level battery...that activates when heated......test my theory by taking it out of the car ...hook it up to your VOM meter and use a propane torch on the tip and see what happens to the voltage. interesting.

and it the only way to tell if its working or not

And you can get a feel for whether it's good or bad by testing it following the procedure in MENU#4 under "O2 Sensor Testing".

emerydc8 · #39 10-19-2007, 01:12 AM

While I am waiting for the rubber boot to arrive for my MAF, I hooked the autometer up to my car to check the Lambda. It was consistently between 48%-52%--both at idle and 2500 RPM. Does anyone know what this plug is with the numbers 052 stamped on it? It's on the right side of the engine bay.

JimF · #40 10-19-2007, 01:36 AM

Quote:

Originally Posted by emerydc8

While I am waiting for the rubber boot to arrive for my MAF, I hooked the autometer up to my car to check the Lambda. It was consistently between 48%-52%--both at idle and 2500 RPM.

That's perfect! Where did you get the connection points?? You may be able to find the connections in the 38 pin Diag Connector on pin 14 for late '94 and and on.

Quote:

Originally Posted by emerydc8

Does anyone know what this plug is with the numbers 052 stamped on it? It's on the right side of the engine bay.

That looks like the connection from the ETA via its flying cable.

emerydc8 · #41 10-19-2007, 01:53 AM

At what I think is X/11 next to the purge valve on the left side of the engine. I think my car was made in November 1992. I put the red on pin 3 and the black on pin 2, selected frequency and it came up as a %. Is that right?

Do I have an ETA? I thought my car just had the mechanical linkage. Maybe I'm confusing the two. In any case, I unscrewed the plug with the engine running and the idle increased.

JimF · #42 10-19-2007, 10:08 AM

Quote:

Originally Posted by emerydc8

At what I think is X/11 next to the purge valve on the left side of the engine. I think my car was made in November 1992. I put the red on pin 3 and the black on pin 2, selected frequency and it came up as a %. Is that right?

Looks good to me . .

Quote:

Originally Posted by emerydc8

Do I have at ETA? I thought my car just had the mechanical linkage. Maybe I'm confusing the two.

I thought that "ALL" MBs had one of those PITA . . . check the connector . . .

emerydc8 · #43 10-19-2007, 08:55 PM

You're right. It's the same connector. Why are they a PITA? Has yours given you trouble?

JimF · #44 10-19-2007, 09:54 PM

Yes, I think they continually are a PITA. . .

Checkout this thread started almost 4 years ago . . .
Yes another ASR problem; '94 S500

Check post #32 . . . and that will bring you uptodate.

emerydc8 · #45 10-20-2007, 01:42 AM

I don't think my car had the ASR option. It looks like the ETA has other functions besides just anti slip.