#Toyota 4runner mass air flow sensor problems manual#
Specs and instructions are in the manual in the ENGINE - MFI SYSTEM - THROTTLE BODY section. That's on the side of the throttle body, and it too can be checked with your ohmmeter. There is another sensor important for the computer's ability to control mixture, and that's the throttle position sensor. Specs for the proper resistance for given temperatures are in the manual. Check the intake air temperature sensor by measuring resistance between terminals THA and E2. There should be no spikes or dropouts of resistance. Make sure the resistance between terminals E2 and VS changes smoothly "in a wave pattern" as you slowly push the vane open. You'll need access to the vane which you get by removing the top of the air cleaner. If you don't have one, google 1993 toyota pickup service manual. Specs and instructions are in the factory service manual in the ENGINE - MFI SYSTEM - VAF METER section. That will tell you if the meter has a problem with any of its circuits, which do sometimes go bad. But the thing to do is to check the resistance readings of the various circuits in the meter with an ohmmeter. That's not to say the vafm isn't causing your problem - it is possible. If you want, you can gently clean the door and surrounding areas with a clean tee shirt and some isopropyl alcohol, but it won't make much if any difference. If you spray any solvents in there, you are much more likely to f*ck it up than help it. Even if the trap door gets a little dirty, it probably won't make any difference. The vafm usually does not get very dirty - I have 281,000 miles on my 20-year-old vafm, and I've never cleaned it and it still works fine. Stupid idea - the vane obstructs the intake of air - but that's what we have. The door is connected to a potentiometer and it sends varying voltage back to the computer to tell of the vane position. The vafm has no wire but instead a trap door (the "vane") which is pushed open by the incoming air.
The wire can get dirty, and that has an insulating effect, so it will start to read low, and cleaning the wire fixes that problem.
The more air that comes in, the greater the cooling, and that is converted into a variable voltage sent to the computer. It has a volume air flow meter, also called a vane air flow meter, which is a different animal.Ī mass air sensor has a heated wire, and the incoming air cools it. The computer can be cleared also by pulling the EFI relay or one of the battery clamps, but the fuse is easier and it won't reset your clock, radio etc.Īssuming you did reset the ecu and you're still getting mixture codes, cleaning the mass air flow sensor would be a good suggestion if your motor HAD a mass air flow sensor. The fuse is in the black fuse box on passenger inner fender. You clear them by pulling the EFI fuse (with ignition OFF) for 10 seconds or so. First, did you clear your codes and reset the computer after installing the O2 sensor? If not, those codes would probably still be in the computer.