A clean mass airflow sensor seems to help

Under the air filter.

 

Can you please tell me what exactly you are shooting with the spray, I have removed the air filter, and dont seem to see the MAFS.

 

The air 'filter' part of the filter is on the left, the other half of the box is the air intake. Look down that hole with a flashlight and you'll see it. looks like a little glass bulb sticking out horizontally.

- D

 

I would say that you need to remove the MAF sensor (by first unscrewing the two screws holding it in place) so that you can clean the two wires. If you can't see the wires, you at best will only be cleaning the air temp sensor which is the amber bulb.

 

http://priuschat.com/forums/gen-ii-...roubleshooting/57617-cleaning-maf-sensor.html

I took a photo of the MAF in relation to the TB. I also posted excerpts from the shop manual

 

So are you guys saying that dirt accumulates on the "clean/filtered" side of the air intake? If so, does that mean the air filter is not that good?

 

In the Atkinson engine, the intake valve stays open until the piston is about 1/3 of the way up the cylinder. This mean some gasoline vapor is pushed back into the intake tract. I think this is what can foul the MAF sensor, not intake air that is unfiltered, but engine air pumped back out into the intake.

Hobbit has a diagram http://www.techno-fandom.org/~hobbit/cars/training/800/atkinson.gif

 

My 2004 has 115K miles. I recently removed the MAF sensor and cleaned it. However the amber bulb looked amber, not grey, so the sensor really didn't need cleaning.

When I lived in southern CA I replaced the engine air filter at 15K mile intervals because the filter got pretty dirty that quickly. In southern AZ the air is generally cleaner and I am now observing 30K mile change intervals.

It is possible that the engine's Atkinson cycle is helping to foul the MAF sensor but I personally have not noticed that. I am wondering if Prius that have a problem with their MAF sensor also have not had their engine air filters replaced at timely intervals.

 

Dirty MAF sensors are not a problem just for the Prius or even Toyota engines in general. As a former Honda owner, I know that some of the Honda websites also talk about the benefits of regular MAF cleaning, and the problems that result from not cleaning them. Also, if you google "MAF cleaning benefits" you'll get hits on a lot of car makers, including VW, BMW, Audi, Ford, etc.

 

Or had chronically overfilled oil.

 

Is this still good advice to just squirt CRC MAF cleaner onto the MAF through the air filter?

How would one know if it’s needed and could it hurt?

 

That would be pretty much car-maintenance theater.

If you look closely at this photo of a MAF sensor, you can make out the two fine wires deep down its throat.



You're not going to get any angle where your sprayed CRC cleaner reaches those wires, unless you take the sensor out of the duct.

The good news is, that's very easy to do.

Cleaning the sensor won't hurt anything (as long as proper MAF cleaner is used, and you don't touch the wires with anything but the sprayed cleaner). It also probably isn't badly needed, if the engine is running well, with no codes about the sensor or mixture, and reasonable fuel-trim numbers.

 

Thanks
Have no issues, no codes, use good gasoline so I’ll just not fix the thing that isn’t broke.