Truck in question is a '95 4Runner, 3.0L engine.

When the truck is running, there's an odd noise coming from the airflow sensor. It sounds like metal on metal contact, sort of like if you took two metal cans and rubbed them together vigorously. Today I did the airbox mod (cut out the bottom of it) and put in a K&N filter. I can hear the noise more clearly after the mod, so it's definitely coming from the airflow sensor.

I noticed the sensor itself has a metal flapper that I assume rotates open as the demand for intake air increases (as the throttle opens). Is this thing known to rattle around or make noises like what I'm describing?

Furthermore, are there other airflow sensors that are compatible with this truck, that maybe aren't so restrictive? I'm new to these trucks, and was excited to do the airbox mod and install the filter. I was disappointed to see how small the rectangular opening is for intake air, and that there's a big metal flapper that has to move out of the way for more air to get by. What's the point of freeing up the intake so much by modding the airbox and installing a good filter, if the airflow sensor itself is so tiny? (rhetorical question!)

Thanks.

 

Mine doesn't make noise so yours is probably bad. Search VAFM and you'll find a few threads where folks have gone to a larger model from one of the Toyota cars. Seems to work out well.

 

BE VERY CAREFUL swapping out VAFMs. You can cause an extreme lean-burn condition with the wrong one. If it's rattling like you said, something is wrong. I'd only swap for the same model.

 

Are the aftermarket replacement VAFMs any good, or is it general practice around here to stick with OEM when it comes to sensors?

 

Mine does the same thing... Just run it till it goes

 

I've found that with any item that is IMPORTANT (hint: VAFM is important) it's best to go OEM....

 

I think the noise could be from either one of two things

either:

A) The bearings or bushings (whichever it has) that the flapper door in the AFM pivot on have worn and is causeing a bunch of movement

OR

B) your idle is WAY too low, and it's making the door not open hardly at all, it's it's bouncing back shut, then open, then shut, then open, then shut, and well, you get the idea...

 

Probably A), since when you crack the throttle the noise gets more vigorous as engine speed increases.

Thanks.