Earthing the MAF

[MORRISMINOR GTI-R]

How do you earth the MAF sensor, im pretty sure mine could need doing but its gotta be worth a try as its running quite rich low down.

I understand the principal of it but which wire do you earth, what type of wire is needed and where is best to take the earth too :?:

Cheers

 

[geetee]

FROM THE FAQ!!!!!

MAF Sensor grounding

First, you'll need a digital voltmeter and a small flat blade screwdriver.

The MAF sensor is located just past the air intake. You'll need to pull back the rubber cover to expose three wires. On mine, the outer two were orange, the middle one is white. The middle pin is where we need to get a voltage reading from (with the engine idling). Take the positive lead of the voltmeter and make contact with the middle wire. The negative lead should be pressed to one of the ground connectors on the engine block, near the firewall, right behind the fuel injectors. You might have to look hard to see them, just look for a bolt with several black wires running to it. Took me a while to spot it myself, several vacuum hoses in the way...

The voltage read should be less than 9mv (.009v), if it is above this value, the sensor needs to be reground. To do this, a wire needs to be run from the middle pin to the ground lug. You'll need to remove the connector from the MAF to get a good angle on it. On either side of the connector is a small opening for a small flat blade screwdriver. There is a wire that runs around the connector to hold it in place, you need to pry this wire outwards, and then move the connector back a bit. Do one side, then the other, and it should pop right off. I'd never seen this type of fastener before, once you have it off you'll see what I mean.

You'll want to solder a new wire to the middle pin, make sure you get a good connection. Then, run the other end to the ground lug. If you want to do the job right, you'll want to get a connector from Radio Shack or other electronics store that has a ring that you can crimp the wire to. I don't remember the size of the bolt, so I'm no help there. I just looped my wire around the bolt twice and put it back on. I may go back and fix it up nice some other time.

Once the sensor is reground, the voltage should drop significantly. Mine was at around 11mv, after the fix it went down to less than 2mv.


GeeTee 8)

 

[celm]

what is the purpose of grounding the MAF?

 

[geetee]

It seems to be quite a common problem that the MAF ground connection becomes "dirty".

The resistance on the ground connection causes dodgy signals to be sent to the ECU - resulting in rubbish idling and poor running generally.

I've tried the above process myself - but my multimeter doesn't work in millivolts - so I have no idea if I have the prob or not. But I'm just trying to sort a high idle...

Cheers
GeeTee 8)

 

[krikra]

My R has a bad idle so I tried the above procedure.
The reading was 80mV when idling!! Between midle pin and BATTERY earth...
Looks like I'll be earthing my MAF soon..

But why do you have to messure the voltage to the earth connectors on the engine instead of just using the batteri earth? And then again why does the new MAF earth wire has to be taken from the engine earth connectors instead of battery or somewhere else more accesable?

 

[GazTi-R]

You are measuring the voltage drop by doing this, or more precisely the impedance in the cable that runs to ground. In theory it would be ideal to run all grounds back to the -ve battery terminal instead of using the engine block(aluminium) or chassis/bodywork(steel) which is not as good a conductor as copper. But in practise this would be messy and heavy, so should be limited to voltage-sensitive components, usually critical sensors.

 

[krikra]

Doooh.. I know what I am messuring

My question was; why use the engine block earth connector (as discribed in the FAQ section) instead of the battery ve- ? Was just wondering if there is some logic explanation for using this hard accesable connector on the engine block :?: