HELP!! Car is running awful at highway speeds

Have you noticed a decline in gas mileage?

 

I am going to follow this post. It irritates me that Toyota refuses to look at a car is there is not CEL illuminated. I had issues early on with my gas mileage, the ECU was replaced and problem was resolved - but they told me the car was just fine and that 36 MPG was great gas mileage for the car (with a combined EPA rating of 50)...

That all being said - lately ( and I am at 4500 miles ), I have had a few instances where there was a noticeable amount of lag on acceleration, almost like it did not realize the pedal was pushed down. I have had it happen only 2 or 3 times and blew it off as no big deal, but the third time I started to get concerned. This sound similar to what you are experiencing. Basically I have experienced it from a stop light, I press the pedal, car goes 2 miles an hour for about 10 feet before the engine/motor get the car moving. It does not happen regularly, but one of the time it did happen I was flooring it to cross a highway with oncoming traffic, and it almost caused a T-bone accident where I would have been hit at highway speeds - scary...

That being said - I have not noticed a decrease in gas mileage, it does not feel like its an issue with the engine/motor - I think i would be able to notice that, but rather an issue with pedal mapping or pedal response, I come to this conclusion since the engine does not rev up at all.

 

After 6 months on PriusChat I'm truly amazed about what I've read of dealerships...

I gather it's a similar situation with other car makers but specific to the Prius, the technology seems way ahead of all the dealer-foolery/capacity to deal with it.

And yesterday I was trying to think of what Toyota must deal with when it comes to all these dealers eager to generate revenue regardless of customer satisfaction/quality of service.

I can barely imagine the kinds of false claims and scams that Toyota has to vet from all these dealers...

If anyone has any links about Toyota yanking licensing from corrupt and incompetent dealers, it might be good ammo for the original poster and the rest of us to bring with us when we have to take our complaint to the dealer's owner...

 

I had a friend on the inside at a dealership other than the stealership where I purchased my car. He specifically told me that it was against Toyota policy (corporate - not dealer) do do this without a CEL illuminated on the dash so to protect this person I have choose not to name the dealership or associate. That all being said the ECU change had a dramatic increase on my MPG (from 36 MPG to 50MPG) but this acceleration lag has only started recently (on new ecu) and I have not spoken with anyone about the issue. I will be at the dealer for my 5k maintenance in a few weeks and will talk to them about it then. I know that they will tell me - "not sure - everything is fine with your car", and think that I am crazy - thats just how it works these days. As soon as my complimentary toyota care service is up - I will probably never go back to the dealership for maintenance again.

 

Have any of them driven your car? Did you ride with them? It's hard to understand how they could drive a car in the conditions you describe and then say nothing is wrong.

 

Could you have sucked up debris like a plastic bag that could have partially clogged the intake tract?

 

I would think that would throw a code when the air sensor showed reduced amounts of airflow relative to the throttle position, but definitely a good thing for OP to check. Since my lag issue I have experienced is sporadic its unlikely that its an airflow issue - but I will take a glance at my intake when I get the car home for peace of mind.

 

+1

IIRC, you need consistent fuel, air, and ignition source for smooth running ;-)
In your troubleshooting, you should also confirm that these problems don't exist:
* Water in one/more of the sparkplug depressions. (Shorts the plugs.)
* Bug or other debris on the MAF sensor (It sounds unlikely, still it has been the
a source of much frustration on GEN IIs. Ensure air filter is correctly mounted.)
* Clogged fuel tank vent. (This is a WAG. For fuel to leave the tank -- no bladder --
air has to be admitted to the tank somehow/somewhere. Perhaps the tank was
overfilled and a small charcoal canister is fouled. I haven't seen a diagram of the
Pc's fuel system so I admit this is probably the most unlikely cause.)

 

It is true that dealership technicians only follow trouble codes. If codes are not set, then there is no problem. It would take almost an act of God to get them to pursue a problem that did not set a code. As already suggested, the root cause of the problem could be an obstruction of the air intake for the engine or an obstruction of the cooling air intake for the battery pack below the back seat. Either one will affect acceleration and gas mileage without setting a code.

I don't understand your description of the accelerator pedal as being "stiff". The pedal is just a linkage to a simple "volume control" that is similar to that used on a radio. How could it be stiff? It either moves or it does not.

 

Maybe the muffler valve is stuck closed?
For the case of dellrio, the valve might be stuck closed intermittently?
A modest increase in exhaust back pressure can have a significant impact on engine performance, and will not necessarily set a trouble code.
I never actually came across a confirmed stuck muffler valve, but would be open to the possibility.
All current Prius models have a 2-way exhaust control valve built into the muffler.
The information below is from the 2012 Prius C New Car Features Manual:

(b) 2-Way Exhaust Control System
(1) A 2-way exhaust control system is used. This system reduces the backpressure by opening and closing a variable valve that is enclosed in the main muffler, thus varying the exhaust backpressure.
(2) The valve opens steplessly in accordance with the operating condition of the engine, thus enabling quieter operation at lower engine speeds, and reducing backpressure at higher engine speeds.
(3) The control valve is enclosed in the main muffler. When the exhaust gas pressure overcomes the spring pressure, the control valve opens steplessly in accordance with the exhaust gas pressure.
(4) When Control Valve is Closed (Low Engine Speed)

• Since the pressure in the main muffler is low, the control valve is closed. Hence exhaust gas does not pass through the bypass passage, and exhaust noise is decreased in the main muffler.

(5) When Control Valve is Open (Middle to High Engine Speed)

• The valve opens as the engine speed and the backpressure in the muffler increase. This allows a large volume of exhaust gas to pass through the bypass passage, thereby substantially decreasing the backpressure.

Text in Illustration

*1
Control Valve
*2
Main Muffler


Control Valve Open

Control Valve Closed


Control Valve Opening Direction
-
-

 

Actually, I came across a GenII with a shop towel sucked into the air intake hose near the coolant reservoir. This car had a SEVERE lack of power, would run the battery into pink bars, then crawl along at max 25mph. No check engine light, no DTC.

 

Interesting regarding the muffler valve, my 02 Maxima had something like that as well.

 

If it was me I would start tracking the state of charge of the Hybrid battery. Is it consistently low even if taking an easy highway ride at 50 mph's for a few miles? And then if its fully charged how long does it take to make it low around town.
In a Gen II with that complaint the Hybrid battery would be on very low. Then the engine has to so all the work and the car is a dog.

If it really bugs you talk the dealer into taking it for a ride with there Techstream software laptop plugged in to check Hybrid battery charging and balance. Most will not unless they charge you there $125 diag fee. Which will be refunded if there's an actual issue.

Oh and check your tire pressure asap. Tires may be super low as they are breaking in and pressure will move around alot for a while.
Put them at 42 front & 40 rear. On these little Hybrids its all about tire pressure.

Good luck and let us know.