Throttle Body Cleaning Question

Unless it is really dirty - cleaning a throttle body generally doesn't improve overall MPG. It does improve the idle quality considerably though, so it is still a worthwhile maintenance step if you can spare the time.

Note that your throttlebody is a DBW type - so you cannot force that throttle blade open to clean it. Easiest way for a DIY is to set the ignition to ON and open the throttlebody plate via the accelerator pedal. You can prop it open with a brick or stick - clean it, then let the accelerator pedal go. Pushing it manually can cause the TPS to read incorrectly, usually have to do a throttle recalibration afterwards to get the car to run right. Other option is to take it to a dealership / shop and have them clean it.

In either case - the idle could be potentially worse for a little while, until the car relearns / adjust for the difference in flow. Could idle low, idle high. or even stall. Don't be too concerned, that is normal behavior. When you have to worry is if doesn't adjust and the car consistently runs poorly - then you'll have to take it in to be recalibrated, etc.

Sure, you can force the throttle plate open, but it may require a throttle recalibration scheme. The throttlebodies on my 2009 Rav4 and 2009 Matrix are very similar in design to your 2005 Corolla (DBW). If I forced it open, i an guarantee you that they will not run right again, until I run a calibration step afterwards. I know some owners have used the no key method and didn't see any issues, but doesn't mean that will be the case for you. Some people have gotten lucky with cleaning the throttle plate by opening it manually - but I cannot say for certain that you will not have any issues if you do so. Each car is a little different.

To err on the safe side - use the accelerator pedal to actuate the throttle plate. The procedure I use (throttlebody on car) is key turned to ON, engine not running. Use a stick and wedge between the throttle pedal and bottom of dash, or have someone stand on the pedal. Throttle plate will be OK and you can clean around it. After cleaning - the car will rev up and idle high for a minute or two until it relearns (1500+ RPMs). Sometimes it will high idle until you drive it around a bit - but eventually it will come back down. Another option is to pull the negative battery terminal after cleaning the throttlebody. It will clear all the learned parameters and it will start from a baseline tune. This case, the car may want to stall or try to stall on startup. Again, same as the other method - car will have to relearn parameters before the idle goes back to normal.

Pretty much - best to spray the cleaner onto a rag or similar. Spraying the cleaner directly may not be enough to get all that gunk off. Also note that most of the deposits are "behind" the throttle plate.