Please help! Dealer is worthless. Major mpg drop.

OK.

The Prius achilles heel is it's 12volt. They generally last 5 years 70k/80k miles, sometimes more. When they fail they fail and one of the main symptoms of that is a drop in economy. They are a cheap fix. It might not be your 12v but it's easy to check and you say you're not sure if yours is the original. If it is, then it is well over due to be replaced.

Leave the car overnight and then in the morning get in and put the car in Acc mode (NOT into Ready). Now wind all your windows down at once and then back up again. Do they go really slow and do the interior lights go dull? Now put the car in Ready mode and do the same. If they now go really quickly, then your 12v is on its way out. Get it changed.

A traditional car shows a failing 12v by getting slower to turn the engine over in the morning over a few days. In the Prius it works and then suddenly doesn't.

Let us know who you get on.

 

driving-mr-mel,

Thank you for filling out the questionnaire!

Try running the test that is recommended here on Prius Chat and report back all three values you see on the MFD.

Look at my signature file below. You will see four links there (Blue Text). Click on the first link. That will take you to the page where the test can be found.

I too tend to think your 12 volt could be contributing to part of your problem. But cannot confirm that until you run the test.

Concerning the spark plugs, I have a feeling the dealer did the right thing there. Plugs are normally recommended for change at 100K to 120K on the odometer. Since you mentioned the check engine light on and or flickering I would suggest trying a different dealer and asking them to pull the codes and tell you what codes they see. Then if any codes come up, please post back the codes they tell you.

Also have you at any time cleaned your throttle bore or MAF on your Prius? If not, you are well overdue for that service. A dirty throttle bore and or MAF will cause engine problems and poor gas mileage. Please take the time to check your oil with the dipstick. If over full it could cause problems. Under full could also cause problems The Prius oil level is best if kept just below the dipstick top dimple. Over the top dimple means there is TOO MUCH oil in the engine. Under the bottom dimple means there is TOO LITTLE oil in the engine. Both of those scenarios are not good for the Prius and will contribute to undesirable operation.

I won't comment on the tires at this time other than the fact that your pressure is a little low imo. Also, I don't recommend mixing brands but a lot of folks do due to budget restraints.

Best of luck to you.

Ron (dorunron)

 

Dealer changed the spark plugs, now the car is sluggish, what plugs did they use, it matters
It's a gen2 how full is the oil, if it's overfull, it's problematic.

 

could be your hybrid battery, but that should throw a code.

 

Everybody hit the nail on the head, but to summarize it for the OP:
1) Test your 12v battery ASAP and post back the results. Learn how to do this here:
Weird stuff happening? MPGs dropping? Test The Battery | PriusChat

2.) Check your oil level ASAP. If it is overfilled, bad news bears.

3) Get the tire psi's higher if you are comfortable. Most here put the front tires at 42psi and the rears at 40psi.

4.) If you dont already, you should be blocking your grill during the wintertime, if it gets below 40f. It will help keep heat in the ICE, which in turn will run less, increasing your mpg's.

I personally noticed a small gain in mpg's when I cleaned my MAF sensor. Learn how to do that here:
Cleaning Mass Airflow Sensor Instructions | PriusChat

Last but not least, keep your HVAC on "AUTO" and set the temp to 72. I noticed that if you set the heat manually, the ICE runs a lot more. I have a 2007 with 80,500 miles and am averaging 46.3mpg this tank, I am farrrr from a hypermiler - I am a relentless leadfoot. I drive 85mph+ on the highway. And Im in Michigan (freezing cold). All of the stuff listed above are things I do/have done that I credit to my good winter mpg's.

 

can you hear the hybrid battery cooling fan more than usual? does the battery meter behave the same way it always has?

 

We're here for ya!! Also for info on how to clean/inspect the MAF sensor, follow this link: Cleaning Mass Airflow Sensor Instructions | PriusChat

Good luck!! The stuff we all talked about here and that I summarized are all very easy DIY stuff to check. Hopefully we can get you back on track.

 

The link below details how Hobbit used to do his throttle bore. It is not really necessary to remove the throttle body from the engine, but it is a very good idea to keep as much fluid out of the throttle bore as possible.

I am really surprised a dealer has never offered or recommended the service. Most of them do that on a fairly regular basis. It is a good idea to keep the throttle bore and the plate in the bore as clean as possible. When it gets dirty, it tends to stick and cause problems.

Also if you don't maintain the throttle body, and it gets to the point where it won't work properly and you have to replace it, you will find the throttle body is rather expensive.

Study the following link. That will give you an idea of what we are talking about.

http://techno-fandom.org/~hobbit/cars/tb/service/

If you don't feel comfortable with cleaning it, take the Prius to the dealer and pay the man for the job. It is money well spent. Have them clean the MAF while they are there as it will be very easy for the tech to do that job while the throttle bore is being cleaned.

IF you clean the MAF yourself, make sure you remove the MAF from the throttle body. Don't rely on these simple sprays you buy to spray down into the bore. Sometimes they work, but sometimes it just causes more problems. It is best to remove the MAF before it is cleaned and then put it back into place. Also make certain you use "MAF Cleaner". Don't use carb cleaner or anything else on a MAF.

 

Your 11.9 on the battery might be a bit low.
If it is over 4 years old, might as well replace it.
Cost should be a bit less than $200.

After that, someone needs to give the service people a kick in the nice person at that dealership.
NO stored code is totally meaningless......and every time that light goes on it probably stores a code again.
Is there no other dealership in your area ??
If not, maybe a call to the dealership OWNER or to Toyota would be helpful.
Most service order writers are about as skilled with cars as the bag boy at the local grocery store; many "service managers" too.

P.S. The gas filling thing might be a critical clue. Sometimes the "vapor recovery system" fails and won't allow a full fill, unless you do it REALLY slow. On the other side of that coin, how do you KNOW that it is not getting full ?? Gas gauges on some older models are a known problem area. If you can't be sure of how full the tank IS.....how are you calculating your gas mileage ??

 

I understood a 12v was on its way out when registering anything below 12 volts and should be over 12 volts even with headlights on. Shouldn't they sit at 12.4 volts normally and 14.5 volts when charging.

I'd say a reading of 11.9 volts is a little low, though probably not enough to cause the issues described.

 

One of the simple possibilities not mentioned is the gas cap. If the gas cap is not sealed properly a code can be set via the evaporative emissions system. Slight chance, but something to check. Won't help your MPG.

 

Please don't forget about the throttle bore and MAF cleaning. If that has not been done, it definitely needs to be.

Your battery is weak, but I don't think that is causing the trouble you have. Do I think you should replace it. It won't hurt, but I really think your problem is like you said. Fuel related. A dirty throttle bore and MAF can cause low MPG, poor response (sluggishness) and loss of power. Remember you commented about 70 being painful and poor acceleration.

I also agree that the gas cap might be a problem. Until you get the codes, we are really guessing.

However due to the fact of age, miles and service work NOT done on the throttle bore and MAF, that is something that should be resolved and could very well be the source of your trouble.

 

Whichever shop you visit next, you need to calmly and as precisely as possible list ALL of the current problems.
Dash light first and foremost; if you have a previous service invoice where they recorded the previous code that might help too (fat chance of that probably).
Not running good; lacks power.
Gas not filling right.
Poor mileage (don't mention that first or their ears slam shut and they don't hear the rest)

Also do NOT mention the other services that have been done because those things didn't affect the present complaints one way or the other.

You may have more than one problem now.
It is good to address each new problem as it comes up..........to head off mass confusion down the road when all of the symptoms meld together in one big mess.

 

Hello driving-mr-mel.

I had the exact problem you described with my 1999 Subaru impreza - the check engine light went on occasionally, the car would not let me top up the tank to 100% and my mileage went to hell.

I explained this situation to my best buddy who works at Toyota and he hooked up a sensor to my car and found the error code and concluded that the emissions system on the car had a fault. Apparently, I caused the problem by constantly overfilling (or overtopping) the tank at the gas station and this flooded the charcoal canister filter. Because the canister filter was flooded, something in the canister distinigrated and corrupted the fuel system lines which caused a loss in power. The canister filter's malfunction vented gas into the atmosphere which caused my loss of MPG. Also the flooded canister filter prevented the car's tank from being able to be topped up to full.

In the end, I sold the impreza because it needed new tires, timing belt, brake service collision repair from a hit-and-run as well as a host of other fixes. I wasn't prepared to sink a few thousand on a car that was 15 years old so I sold it and never fixed the problems.

What I would do at this point is find out what the error code was for the check engine light that came on previously for your car. I think the on board computer stores a history of error codes. Mine was P0440 and my buddy knew right away it was something to do with evap. emissions control. From there on, you can start eliminating and trace down to that problem that caused it.

Good luck!

 

I would change the 12v asp. 11.9v is 80% depleted from what I have read. H