Cleaning MAF Sensor

[andyprius]

I bought sensor and throttle body cleaner and can says to remove sensor, saturate then dry good. My Bentley book says the sensor has a platinum wire, so ...should I remove the sensor? how ( without damaging anything ) Since the device is basically plastic I am always leery of putting on excessive pressure. ty. andy.

[Patrick Wong]

Hi Andy,

I suggest leaving the MAF sensor alone unless you have a driveability problem. Use the plastic wand that comes with the throttle body cleaner so that you can direct the cleaner onto the throttle body plate (rotate open with your hand) and the throttle body interior.

Since the throttle body cleaner typically leaves an oily film (to lubricate the throttle moving parts), it is not clear that this is suitable for cleaning the MAF sensor.

[andyprius]

Originally Posted by Patrick Wong

Hi Andy,

I suggest leaving the MAF sensor alone unless you have a driveability problem. Use the plastic wand that comes with the throttle body cleaner so that you can direct the cleaner onto the throttle body plate (rotate open with your hand) and the throttle body interior.

Since the throttle body cleaner typically leaves an oily film (to lubricate the throttle moving parts), it is not clear that this is suitable for cleaning the MAF sensor.

OK Thanks Pat. Actually the Product I have is what was recommended: MAF Throttle body & sensor cleaner. After Jay's input the question is: " To do OR not to do" OOps, I stand corrected, it is only sensor cleaner, altho I washed the walls and butterfly valve with it also. With a good strong light I was amazed at how much dirt collected on the horizontal butterfly valve.

[jayman]

I tried to post earlier, but the site went down

Anyhoo, here are factory shop manual prints of the throttle body and the MAF. The MAF is easy to remove, you unclick the connector, remove the two tiny philips head screws (Don't drop the screws), then wiggle out the MAF

[jayman]

GEE-zus what is wrong with the site? SLOOOWWWWWW

This is a photo of the MAF before cleaning. I couldn't get a clear photo of the hot wire guts, but the bulb thing is the temp sensor. I theorize that layer of ash is the oily residue from the PCV system. Both my Prius and my FJ have it

[jayman]

The MAF after cleaning. A big difference. The ash-like stuff was also coating the two hot wires inside the MAF. It only took a couple of spritz applications to the RTD bulb, and the MAF wires, to get them squeaky clean

[jayman]

Here is the only clear photo I have of the MAF guts, after cleaning. Obviously, somebody with a better camera will be able to get better photos. You can see the ash deposit is gone and the two hot wires are squeaky clean

When I cleaned the Prius last fall, there was perhaps a teeny bit of difference in how it ran. With the FJ, a much more noticeable difference

[jayman]

For reference, looking straight down at the Prius airbox, with the lid removed. You can see the MAF and below, the closed throttle plate

[jayman]

It would be best to remove the MAF before cleaning the TB, to avoid TB cleaner residue on the MAF hotwires. With the MAF removed, use one hand to open the throttle shaft at the return spring

Be gentle opening the blade, as the TB is electric drive, same as on my FJ. With the blade fully open, use a few gentle sprays from the TB cleaner. More is *not* better! Get too much cleaner into the intake, you could have a no-start, or a very poor start

Eg: when I cleaned the TB on my FJ last fall, it clearly needed it, along with the MAF. There is no external return spring on the FJ throttle body, so I had a neighbor kid sit in the driver seat, with the motor off and ign On, keeping the gas pedal floored. You can NOT use this procedure with a Prius, once you power on and floor the gas pedal, the gas engine will try to start

While the little bugger kept the pedal floored, I used the TB cleaner to spray off the heavy buildup from the blade and passages inside. I'm pretty sure I used to much cleaner, as once I had everything together, it was hard to start and ran roughly for a few minutes

However, once it settled down, and I went on the highway to blow everything out, there was a very immediate and apparent difference in how my FJ ran

Note, if the MAF has never been removed before, the o-ring might stick. Gently wiggle it out, don't use a tool to try to pry it off.

[jayman]

I am leaving tomorrow morning on a business trip, will be gone about a week. Any questions will have to wait until then