Just clean up the plugs. Burn the deposits off with a propane torch. The following worked for me! Okay. Some folks suggest cleaning out the throttle body as the first step in diagnosing any improperly running Nissan/Datsun (my own experience with a routinely maintained - not obsessive compulsive - L24e, after 178000 kms the TB was spotless, but NOTE absolutely no oil consumption). If the MAF has never been replaced, you are most likely looking at it having some significant wear on the potentiometer carbon trace. But not to worry, because with a very little bit of work you can extend the life by at least a factor of two. You will need some rudimentary test equipment - a digital VOM - can get a cheapie from Radio Shack or Canuck Tyre. In order to work on it, it is easiest if you remove the MAF from the car. The pin numbers are clearly marked on the outside of the connector. First do the routine checks on the resistance between pins 33 and 34, this should be somewhere between 100 and 400 ohms. Next measure the resistance between pin 34 and pin 35, this should be between 200 and 500 ohms. With the entire assembly at a nominal temperature of 68 F (20 C) measure the resistance between pin 25 and pin 34, this should read below 2900 ohms (colder temperature should yield resistance above 2100 ohms but less than
2900). Now the hardest part. You have to remove the plastic cover from the bottom of the MAF. Nissan just glues this on with some sort of silicone based sealant. To do this you will need a very sharp knife and a wee bit of patience. I used a box cutter knife - yes of the terrorist variety - and just slid it along each joint, keeping the blade as tight against the aluminium case as possible. Take your time and do several passes, because you want to remove all of this adhesive material and get under the edge of the plastic cover about 1mm (1/16th inch). You can also use something like a dental pick to scrape the sealant from between the case and the lip of the plastic cover. Once you've done this it is possible to gently pry the cover off the case. Underneath you will find the potentiometer and a circuit board about 3 x 1 inches (7.5 cm X 2.5 cm). The wiper of the potentiometer runs along the carbon trace on the edge of the board. You will see that the wiper is split and each segment has a small bead that forms the contact with the carbon trace. You will also notice that over time this bead has worn a groove in the carbon trace. You can measure the resistance across the potentiometer, as you move the flapper on the MAF. You will see the resistance go up and down several times on the full range of motion of the flapper. If in doing this you see the resistance go to zero ohms, you will know that the wiper has worn its way through the carbon trace and is contacting the substrate - this just confirms the MAF diagnosis. All you have to do to fix the MAF is to shift the location of the circuit board every so slightly so as to get the potentiometer wiper to contact, previously untouched carbon trace. Loosen, but don't remove the three screws that secure the circuit board to the housing, sufficiently that it is easy to shift the circuit board. Now you should be able to push the circuit board towards or away from the connector, whichever is easiest for you. You should be able to shift it 0.5 mm easily in either direction. Hold the circuit board tightly in the direction that you have shifted it and carefully re-tighten the screws. To see that you have affected a change. Test the resistance across the potentiometer as you move the flapper. You should see higher resistance values than initially, and you should not see any zero ohm readings. Fixed! Before you glue the plastic cover back on make sure you clean out the housing of any little bits of residual sealant. Clean off the gutters on the plastic cover, and the outside of the housing. Take a quick-clamp (IRWIN) large enough to grip the girth of the MAF and use it to hold the plastic cover onto the housing. Then apply either an acrylic sealant/cement or a polyurethane cement as original. Allow to dry. Reinstall and enjoy driving your practically new car!! Note - Given the dimensions of the carbon trace it should be possible to employ this technique at least twice before contemplating replacing the circuit board (part # A31-8412RA 3706). That works out to approximately
450000 km life for the average dinosaur MAF.
-bob