MAF Sesor connection: clean and BWAAA

Normy · 04:41 AM

Anyone else have this problem?

Or these symptoms?

-I have a PLX O2 sensor installed in the glove compartment. If I pull the MAF and clean the connector on the device and the connector on the harness with deoxit... immediately the car runs totally different.

Prior to cleaning, the car will feel a bit down on power, and you can smell the exhaust at stop lights. I normally drive with my windows down, so this kind of sucks. The air-fuel meter will register in the 13:1 range in normal driving, and down around 10:1 to 11:1 at full throttle! Oink, fuel mileage goes into the single digits in town.

Now-

Clean those connectors, and voila! Suddenly, I'm running between 15:1 and 16:1 in normal driving, and at full throttle it sits at a fairly solid 12:1 to 13:1. Fuel mileage goes up...and the car turns into a raging animal. Almost no smell either.

[note: I have a rising-rate fuel pressure regulator, and as a result I've set the idle mixture at 100 ohms, which is very lean]

I'm serious- these days, I can pull the MAF in 15 minutes, since I've had so much practice. All you need is a 13 mm socket to unbolt the airbox, and then I lift it and the MAF out together, pull the two plugs, and spend 5 minutes cleaning. Replacement takes another 15 minutes, and BANG! Different car~

I usually have to do this about every 2-3 months. Solves the problem....but it makes me wonder. I don't think that Porsche intended to build a car that needs its' MAF connector cleaned every 10 weeks-

1. Has anyone tried this on their LH-injected 928? If you are having driveability problems, it might be a good idea.

2. Any ideas as to why this would be true? The MAF is in perfect working order, rebuilt a few years ago by John Speake.

N

lizard928s · 07-02-2009, 05:27 AM

check the rubber seal in the MAF plug. Make sure it is there.

After the next cleaning put some dielectric grease in the plug and MAF connector.

Danglerb · 07-02-2009, 08:01 AM

Three extra variable to consider;

PLX 02 sensor faking a narrow band signal.
Rising rate fuel pressure regulator altering fuel pressure way beyond normal limits.
Idle mixture set lean.

Brain is Euro or modified Euro?

Could be something flaky in the wiring, and it needs wiggling around every few months.

John Speake · 07-02-2009, 08:50 AM

You still having that problem Normy ?

Have you tried just disconnecting the battery ground for a few seconds ?

Normy · 05:08 PM

I have NOT tried that.

Nor have I tried removing the MAF plug....and simply putting it back in. I always use the excuse of pulling the MAF to clean the contacts.

Hmm, It might sound stupid, but I haven't tried simply depowering the whole system, or at least the MAF for a few seconds- I've always either chased my MAF or if the battery was interupted... ignored its effects on the system.

Well. You learn something every day-

Tomorrow, I will try removing the battery, and then watching the PLX screen. I suspect that Senor Speake's thoughts are incorrect; my MAF works fine [it should; it came from John's car!], I just have a connection that slowly corrodes.

John-

The MAF connection: how sensitive is this? When you sent me your MAF, I used a file to make sure the connections between my wiring harness and the MAF from your own car had a good connection.

Question: Do you think that my continuing problem with this connection had something to do with me filing down your work in Orlando? I filed the connections on your MAF.

N!

John Speake · 07-03-2009, 12:59 AM

Hi Normy,
Well, you will have taken the plating off the MAF pins, but they should be OK if they are clean. Add some vaseline or dielectric grease for protection.

Do they look corroded when you clean them ?

The cableform sockets are much better quality, and I've never seen problem with them.

Normy · 07-03-2009, 02:29 PM

Quote:

Originally Posted by John Speake

Hi Normy,
Well, you will have taken the plating off the MAF pins, but they should be OK if they are clean. Add some vaseline or dielectric grease for protection.

Do they look corroded when you clean them ?

The cableform sockets are much better quality, and I've never seen problem with them.

When I clean the contacts...they look PERFECT. At the same time, the voltage that flows through these contacts is minuscule- You're the expert, tell me what it is, but I doubt it is any where near 12 volts that the system operates at.

I'm serious- all I do is spray deoxit on the contacts, and everything is suddenly copacetic. I can't simply "pull the plug apart, and then put it back together", because I just cleaned it. 10 weeks from now, if it starts running rich I will do that, and I'll post that here.

Are the prongs gold-plated? If so, then I need a new MAF. I've already tried coating the plugs and the connectors with dielectric grease, and covered the connector with 1/4 inch of black electrical tape-

Thanx 1000 times John!

N!

Danglerb · 07-03-2009, 03:01 PM

Maf signal voltage is I think 0-9v?

A tiny amount of corrosion and I think it would effect how the car runs, actually what I wonder about is how it could be just a "little" off instead of way off.

Maybe some issue with the harness?

Normy · 04:20 AM

Quote:

Originally Posted by Danglerb

Maf signal voltage is I think 0-9v?

A tiny amount of corrosion and I think it would effect how the car runs, actually what I wonder about is how it could be just a "little" off instead of way off.

Maybe some issue with the harness?

That is the point of my post.

Danglerb · 07-03-2009, 05:11 PM

A lot of people are already into holiday weekend posting mode, servers may be getting overloaded.

John Speake · 07-04-2009, 01:00 AM

Hi Normy, the supply voltage to the MAF is 12v. The supply current involved varies as the airflow increases, but it's not mopre than a couple of amps.

The contacts on the MAF are tin plated, nothing fancy. They are designed to be self cleaning when the plug/socket pair are mated/unmated.

Try the battery disconnect as I suggested earlier.