Why does my MAF start working when I "tap" it? - PeachParts Mercedes-Benz Forum

brookspw · #1 08-25-2009, 11:31 AM

Been having all kinds of surging/rough idle/bad mileage issues. Checked vacuums, fp regulator, purge valve, etc. MAF replaced in march. Ran fine for a month or two then back to the same.

Car was surging at idle, I was looking for vacuum leaks, I said "What the heck" and tapped the MAP body right under the connecter. The idle immediately increase about 2-300 rpm then settled into a perfect idle.

This will last all day sometimes, other times it will last 5 minutes. But...amost always I can make the idle smooth out by doing this.

I have checked the connections, wiring, seal, etc and all seems fine. Is this just a MAF with a bad connection or something inside it or is there something else I should check?

Seems like I found the problem...but don't know which angle to approach it from.

Advice?

brookspw · #2 08-25-2009, 03:05 PM

No one? .

I have doublechecked the connections, wires, etc. Is there a contact or something inside it? I know that my original OVP would do that but never understood why.

brewtoo · #3 08-25-2009, 04:08 PM

Some modules are known for cold solder joints inside. Search for more info.

tinypanzer · #4 08-25-2009, 05:46 PM

Yeah, that sounds like a classic cracked solder joint symptom. Fix is to remove the part, and resolder the joints where the connector meets the board. Only way to know for sure is to open it and inspect.

You could also have a bad connector on the wire side of things, but probably less likely.

brookspw · #5 08-26-2009, 11:35 AM

Quote:

Originally Posted by tinypanzer

Yeah, that sounds like a classic cracked solder joint symptom. Fix is to remove the part, and resolder the joints where the connector meets the board. Only way to know for sure is to open it and inspect.

You could also have a bad connector on the wire side of things, but probably less likely.

I'll open it this weekend and see what I find. Thanks. Would explain why it seems like it works great some of the time but like crap most of the time. When it is working...it is smooth as can be.

brookspw · #6 08-31-2009, 08:33 AM

Well, once I finally got it open...boom, one of the 4 connections (wire pin, same side as red wire) was broken. Soldered it back and, voila, smooth idle. The soldering was no problem.

Anyone know the exact size of the torx head? I had a set...but none were the right size. 15 was too small and 20 was too big.

tinypanzer · #7 08-31-2009, 11:20 PM

Quote:

Originally Posted by brookspw

Well, once I finally got it open...boom, one of the 4 connections (wire pin, same side as red wire) was broken. Soldered it back and, voila, smooth idle. The soldering was no problem.

Congrats! Remarkably satisfying, isn't it?

Quote:

Originally Posted by brookspw

Anyone know the exact size of the torx head? I had a set...but none were the right size. 15 was too small and 20 was too big.

Bizarre - there is no torx size between 15 and 20...... Sure it's not a spline drive? Or, are your T-bits made in China and out of spec (seen it before..)?

brookspw · #8 09-01-2009, 08:12 AM

Quote:

Originally Posted by tinypanzer

Congrats! Remarkably satisfying, isn't it?

Bizarre - there is no torx size between 15 and 20...... Sure it's not a spline drive? Or, are your T-bits made in China and out of spec (seen it before..)?

Well, could be, I guess. Torx with the pin in the middle? Appeared close to the T20.

Yep, felt good. FYI, for anyone else that attempts this, instead of pulling the board out -- cut out the square cover on the other side where it is sealed so you can solder with the board in place.

I also rewired the air pump (emissions). Those wires were shot a long time ago. Except for the CEL it was no big deal. It had never run since I owned the car for 4.25 years. Sounded like a lear jet taking off when it kicked on the first time.