Cleaning Throttle Body

While taking things apart to fix that torque bushing, I removed the throttle body,

Close-up of dirty throttle body

held on by four 9mm bolts to get access to the bolts holding the torque arm in place.  It looked dirty. In the extreme close-up, notice the tar deposits on the top and bottom of the flap. Figuring things work better when clean, although I really don't have proof of such a hypothesis, I decided to remove the gunk before re-installation.  Cleaner specifically for this task exists, so that's what I used.

The Cleaning Job

Clean!

Completely removing the throttle body from the car made cleaning both sides a snap.  I'm not sure what comprises throttle body cleaner, but it melted away the plaque deposits on contact and probably reduced my lifespan by three to six weeks.  Wiped the run-off away and that was it.

If the part wasn't off the car, cleaning would have been much more difficult, as I would have needed to hold the spring-loaded flap open during the process so I could clean both sides.  The part went back on the car when reassembling the rest of the air intake system.  The four bolts were tightened to "hand tight".

Clean too!

Can't really be sure if this made or will make a difference in performance or fuel economy. Maybe the throttle will turn a little easier as I've removed some of the gummy material from the pivot points, so that actuator won't have to work too hard to reposition the throttle.  Since a spring pushes the throttle closed, that won't have to work as hard when closing the throttle.

Rest of intake dirty...

What was still very dirty was the intake itself.  I tried to clean this a little with just a rag, but I think, like the throttle body itself, removal first would yield the best results. Just inside the intake was a sensor, I didn't want to contaminate that with cleaner that could cause damage.

 

 Two observations worthy of note

1. This is a "throttle by wire" car
   A set of electrical wires controls the throttle, there's a servo in the throttle housing to create the force to overcome the spring and open the flap to increase air flow. No mechanical connection between the driver and the device feeding air to the engine. I would bet the engine management software decides how much to open the throttle, the position of the accelerator pedal being just one of the factors in the decision-making algorithm.
   
2. The spring-action of the throttle will result in closure by default
   This is design for graceful failure, I would guess.  The mechanical spring will force the throttle closed by default, so if the actuator in the throttle fails, the lack of air will result in the engine stalling, which seems to be the safest of alternatives.  A neat, fail-safe, design.

I'm not sure how to assess a cost, as I already had the cleaning chemicals on hand and I'm not sure how to account for few paper towels.  For tracking purposes, let's say the cost approximated zero.  RepairPal says this would cost about $200, labor being the biggest factor in the price. This was an easy job, something to consider tackling on your own and saving those two Benjamins for something else.