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MAF Sensor Grounding

red_triangle.gif (202 bytes) Written by Jim Wright

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

MAF Sensor Grounding Q&A

red_triangle.gif (202 bytes) Answers provided by Andy Radin

>When doing the MAF reground, what kind of wire should I use? How much? Do I just buy some wire at an auto supply place?

It's better not to snip the middle wire. Solder to the pin or scrape off some insulation and solder to the wire. That way if something happens to your new wire, it'll still run.

>Do I just snip the middle wire from the MAF sensor and solder the new wire right there or do I need to solder the new wire to the middle pin itself?"

I recommend that you do this RIGHT the first time so you'll NEVER need to futz with it again. I saw one (nameless) list member who crimped on a new wire and just jammed it under the battery tray, wanted to know why his car didn't idle. I had crimped connectors and a galvanized ring terminal, and they corroded. Just last night I redid it with soldered 10-gauge wire and gold-plated terminals. That's way overkill, but I never want to touch the damn thing again. Try 12-16 gauge, whatever's laying around. Use conductive grease on the terminals and get a nice shiny hot solder joint (dull finish means it was too cold and won't conduct well).