My dealer has recommended replacing the "mass air flow sensor" as well as performing "throttle body" service. I'm not familiar with these items and a search here turned up nothing. Does anybody have any pertinent information to share, please?

Thanks.

 

http://en.wikipedia.org/wiki/Mass_flow_sensor

Benton 31jul09

 

I'm no mechanic, but this sounds iffy unless you're having some issues, that and I thought the TCH had multi-point fuel injection, ie. no throttle body

First get a justification for this work from the first dealer, then get a second opinion. If it turns out that the first dealer is less than honest about the recommendations, report them to the BBB, Toyota USA and don't go back.

 

Also, is the shop offering to do the work under warranty? Just about anything in the engine controls would be covered under the 5-yr/50k-mile pollution control system requirement, no? First owner only?

But good question from BOFH. I'm no gear-head, but I've never heard of an air flow meter going bad.

Benton 31jul09

 

Throttle Body Service: That's were they remove the large rubber tube from the air cleaner outlet to the throttle body. They usually a carb cleaner and toothbrush and cloth to clean the insides of the intake.

The throttle body gets dirty from the engine gas recirculation. The gas only versions are set up like this, i'm not sure about the TCH.

So my guess is how many miles would a car have have to require cleaning. If the car tends to jump at takeoff or idles at different idle speeds, then the TB may need cleaning.

I cleaned the old '94 Corolla I had by myself. It's first cleaning was at 150,000 miles. It had some thin black deposits inside the throttle body which wiped off rather easilly using gumout carb cleaner. I had to press the butterfly open some to clean around it. Once done the car ran the same as before and got decent gas mileage.

 

The throttle body will require cleaning on occasion. Do not use carb cleaner if you do this yourself. There is a special coating on the throttle body plates that can be damaged by regular carb cleaner. Pick up a can of throttle body cleaner that is less harsh to do this job.

The throttle plate will "stick" shut when it needs cleaning and as noted above, when the throttle is pressed harder, it will suddenly "pop" open and the engine rpm will surge. This is corrected by removing the carbon deposits under the plate and in the throttle bore.

As for the mass air flow sensor, your dealer is trying to pad his pocket at your expense. They either work or they don't. The check engine light will come on if this sensor has quit working correctly and can then be replaced. Most of them will last well over 100,000 miles before they quit working.

 

Thanks David for correcting me on the throttle body cleaning. Now I know they do make a cleaning product just for this purpose. Any surging, now I know what to look for.

Jimmy

 

No, no offer to do this under the bumper-to-bumper warranty, so I figured this isn't a real repair at all. They said these things are to make the engine "more efficient". Yeah, I'm dying to spend ~$100 to gain .03% in MPG. And yes, I made up the .03%....

 

My car has 32,000 miles on it and I have noticed no change of behavior in 3 years. They "recommended" these items at my last routine service visit.

 

My dealer recommended it as well at the 60,000 mile service. I declined. I did remove the Mass Airflow sensor to inspect and clean it myself. Visually I could not see any buildup, but cleaned it anyway. I used brake cleaner, gently spraying the sensor wire to clean it. After the brake cleaner evaporated I re-installed it. I couldn't tell any change in how the TCH was running, or did my mileage change.

FYI, I used to have a Ford Explorer. The mass airflow sensor would get a buildup of "dust" on the sensor wire after a while. I could always tell as the Ford would start pinging chronically on hills. Clean the sensor, and the ping was gone.