2008 Prius losing power - Need troubleshooting help.

All Throttle body tests I did were in IG-ON (two pushes on Power button without brake) mode, as the software explicitly said asked to do so for its own open/close test. So yes when I manually turned the knob approx. 90 degrees CCW, it was in IG-ON mode.

I would love to get a used Throttle body assembly, test it per factory recommendation and replace it with my existing one, however I would just like to know which screen shot are you referring to that shows 16% variance in positions, just so that after I replace I can verify if that changed.

Here is the screenshot of the inspection procedure.

 

I discovered this "BUZZ" sound coming directly from the throttle body assembly in "READY" mode only (does not come in ACC or IG-ON modes), I recorded it, please turn up the sound as it is low buzz sound, when I touch the knob or the spring this sound changes a little bit, not sure if this is normal, to me it sounds like a motor going bad.

http://youtu.be/Idqg3FHRIBI

Anyhow today when I tried moving the knob in IG-ON mode I saw that the throttle body plate was moving, so tonight I can probably connect the laptop and check for what % opening it reports when opened all the way.

 

And I was thinking those would have been some sensor on the gas pedal, how naïve am I. I am going to manually open the throttle valve in IG-ON mode and check the readings, meanwhile I have already started looking for a used valve. My Ohmmeter is fine, I was just not holding the fuse steadily, I verified the reading with a industrial grade ohmmeter from my work and got the same reading. I will use that to test the throttle valve. Over the weekend I might even go to junk yards and try to find one. Thanks Patrick for support and direction. Will keep posting updates.

 

So finally was able to check the opening by hand today, it did report 65.4% when open full by hand, the valve plate was completely vertical, this was done in IG-ON position, it did not feel tight at all. I discovered that the last time when I had tried to do the same and was unsuccessful, the car as parked for more than 4 hours and hence cold, this time I had already turned on the engine and let it warm, which is why I would think that the car hesitates more when it is cold and then gets better and better. Everything is starting to make sense now. Thank God!

 

Thanks for valuable insights and advises, really appreciate a lot Patrick. I have learnt a lot from you and few other members.

 

Looking at the hobbits page for removal of the throttle body more closely, I noticed towards the end of this article that during the reassembly how the sensors could end up in wrong positions and might need to re-aligned. I am kinda leaning towards first opening this and play with it to see if the variance in the 2 sensors reduces. I wanted to know if you (or anyone else) can provide me the correct numbers of these 2 sensors when the gas pedal is "not depressed" and when it is "depressed completely". Should both read "0" in the first case and "60 +" in 2 second case?

TB cleaning

 

OK so performed the procedure yesterday, had a lot of fun. Removed the throttle body completely. Here are the findings
1) Since I already had throttle body service from dealership, I did not find lot of gummy stuff,
2) Was able to feel in a few occasions that the plate did not return quickly, it definitely was sticking and that is why I was not able to open it the first time when I tried a few days ago and the car was cold at that time.
3) Opened the motor, TPS and the gear system, all looked BRAND new inside, I still went ahead and lubricated all moving parts with some lithium spray grease available in pressurized can (from Autozone). Still sprayed the throttle body tube from both side and while opening the valve completely with CRC throttle body cleaner to clean anything else left out.
4) First upon installing the body back I rotated the sensor clock wise completely till the CW end (originally was at about 35% away from the extreme CCW end). Checked the variance in the 2 Accelerator Pedal Positions and found exactly the same numbers as before (as in post # 78). Idle was OK but when I depressed the pedal it started misfiring every 1 second. Figured this was not the right position.
5) Then removed the throttle body again (within 10 minutes this time) and adjusted the sensor right approximately to where it was, the 2 sensors still at exactly the same numbers with approx with same variance, the engine ran like before, hesitant, misfires during initial warm up time, rough, slight vibration.

So in conclusion, rotating that sensor does not affect the positions of those 2 sensors, but it does affect the running of the engine. Will buy a used one from ebay with hassel free return policy and see how that goes.

Spent almost 6 hours total and I gained some good hands on experience working around the engine for the first time. I am glad I did it.

 

I was only able to get to the outside of the TPS as shown here on hobbits page http://techno-fandom.org/~hobbit/cars/tb/service/13cruft.jpg there seems to be no access point to further open it to expose any electronic circuitry unless one cuts open its plastic body. So I left it at this point, mine was very clean in the middle around moving parts a little bit of dust around the circumference which I cleaned with pressured air and towel. I have already ordered a used throttle body from ebay, if that one turns out to be good I will try to get into the TPS of existing throttle body.

Maybe 10% better and hence I feel the car runs 10% better, I don't think the lubricating itself helped but I think cleaning the points with CRC cleaner where the throttle valve shaft meets the cylindrical tube helped a little as there might have been some left over gummy deposits.

Yup I had bought a new gasket based on your advise from post # 58, the gasket is not a very common item, the dealership I went to did not have any in stock, nearest other one had only 1. I really wanted 3 as I knew I will be doing lotsa "trial and error" but I settled for one 1 due to availability.

Further more to come!

 

OK here we are, the big day was yesterday. Replaced my throttle body with a used one that I bought on ebay which was part of a 2008 salvaged prius with 70K miles. First before changing I verified the variance of my existing acc pedal position sensors in IG-ON mode, found the same as before (16.0 & 32.1), then replaced the TB and without turning the engine on, checked the variance of the new TB in IG-ON mode, the numbers did not change at all it was exactly the same (16.0 & 32.1) and I got a little upset. BUT!!! when I took it for the test drive, the problem was not there! No misfire upon startup, not much hesitation, power much better, seemed normal. Very happy to get that power back. Thank you very much Patrick for continuous support and direction.

I feel the problem had to be in the butterfly valve or the motor, as even after performing the throttle body cleaning service at the dealers I was not able to freely open the valve by hand on the (my post # 77), and when I actually removed it and cleaned it again it was showing sings of not very lubricated even after lubricating the gears etc. One difference I noticed between mine and the used one that I got is that after opening the valve by hand and releasing it the valve went very fast, so when it hit its end point it would resonate there, the used one I bought did not do that, one I released it would just get closed.

So here is something we can discuss about the TPS and its variance.

1) Variance did not change by changing the position of the TPS on the TB.
2) Variance did not change even by changing the complete TB.

See screenshots.

 

Ok maybe I concluded that very quickly. So I certainly see that 4 out of 6 issues have gone by changing the TB however there are couple more symptoms that still remain, which might be something else.

Here are the issues that seems to have gotten fixed,
1) When the car is cold depressing the gas pedal all the way produced misfires, that is gone,
2) Engine idle was vibrating and hesitating, that is gone too
3) When pushing to gas pedal for gaining more speed, there would be a trrrrrrr sound from the engine, seeming like the engine is working too hard to produce that power, that has got much better, sound is minimal.
4) Bad gas mileage, got a little better (still need to drive for few days to check the exact numbers)

Here are the remaining issues.
1) During cold pickup (in mornings) the battery drains quickly, even if the engine is on seems like the engine is not revving up enough
2) Then suddenly after a minute the engine rev's up and then drives normally, but by this time the battery is almost to the purple.

Possible solutions / Plan of Actions:
1) Will add fuel additive like before and see if that makes a difference, if it does then as you had mentioned before that the fuel injectors might be bad and I might have to send those out for cleaning. Is there any way to diagnose the fuel injectors with mini-vci?
2) Maybe that unchanged variance in Throttle position sensor needs attention. I will check that again tonight and report, meanwhile Patrick would you be able to connect your Mini VCI and check what the readings for the 2 sensors are in your gen 2? I would really appreciate that, that information will be very helpful to compare.