MPG loss, PCV and idling

First, I'm sure you know how to spell nice person-ume. You really need the codes, and the local mechanic, unless they have the correct Toyota software, may not be able to retrieve them.

It's possible to harm the MAF sensor and throttle body with overly aggressive cleaning. On older cars, high idle was one symptom of a vacuum leak IIRC. The PVC valve work may have affected that.

How many miles on the engine, and any noticeable oil consumption? Any new noises?

 

Most likely. In ready mode, you're basically reading the output of the charging system. At rest and under load with the car off is how you should test the battery. 11.9 dropping to 11.5 under a slight load is a bad sign for the 12V. Your car's working extra hard trying to charge a battery that's not wanting to be charged.

But I think it's still a good idea to check the codes with a reader that can get all the codes from a Prius. Happy hunting.

 

11.9 volts with the car off is what I got after leaving the driver's door ajar for about 18 hours, not good at all. That's one thing you should deal with right away. If it's not too old (say less than 4 years) I would try a full charging session with a smart charger, 4 amp range, see how it goes. If older just replace it.

That may be just one of your problems, but worth dealing with asap.

 

I agree the 12V is bad. 11.8 at rest is essentially discharged. But I don't think it'll noticeably bog down your acceleration and cause that much of a drop in mileage. I read somewhere the effect might be as high as 2 mpg, but that wasn't an unimpeachable source, just a guy on the internet.

Did you spray the throttle body liberally with the TB cleaner?

Did you remove the MAF for cleaning?

 

It sounds like you did those projects exactly right--well done. The internet is good for something.

 

Did you also clean and lubricate the throttle butterfly axle and spring while you had the MAF out? Does it move freely?

It may very well be related, depending on where the exhaust gasket that you are talking about is.

I wouldn't worry about the 12 V battery for the moment, that is the least of your worries. Charge it up overnight and then re-test to see if the resting voltage and the voltage under load come up. If not replace that sucker and be done with it. But, like I said, the 12 V battery is just a side issue.

Just to add my +1 to getting the codes, otherwise you will continue to nice person-ume.

 

Anytime you clean the throttle body and MAF sensor it's a very good idea to disconnect the 12 Volt battery for a few minutes to reset all of the computers.

Over time the ECM will make fuel/air trim adjustments to compensate for the MAF and TB as they get dirty. If you clean them without a reset the engine will run rich and it won't idle right. Cleaning the MAF and TB is something we do on every Prius that we work on, no matter what the job is. I've seen cars that wouldn't idle correctly as well as cars that wouldn't run at all (post cleaning) and it's normally proportional to how dirty the intake was before the cleaning.

Actually anytime you do anything to a Prius you should disconnect the 12 volt to reset everything. Make sure that the car is on level ground when you reconnect the battery or else your fuel gauge will be off.

Matt

 

Maybe. But it is definitely low enough to indicate that it's time for a new battery.
Likely that other odd things will start happening too.

Make sure you charge the new one BEFORE installing it.
Then check the charging voltage after installing.....in READY mode (running).

 

You ever fix this?? I wish people would remember to post the solution. So much troubleshooting on this forum and so few came back to say what fixed their problem.

 

from post #10, i think it was the throttle body and maf