TOPIC: Toyota Prius 2006

Ok guys, I need some help.

I've grooved my 2006 Toyota Prius and there was no difference in performance or mileage. Then I capped the PCV inlet and got a sweet whistle and some performance gains, but no mileage increase.

I figure that the problem is the ECU and the Long Term Fuel Trims, have not been reset. I grounded out the system for a day, while I was grooving the throttle body, but there is no key to leave in the ON position and I don't have a scan tool.

Any suggestions?

Hi Will,

One of the first things to check... vacuum leaks, I know from checking on-line that there is one hose going to the evap system. I don't like where it is located but it would be worthwhile checking it for any leakage. Most of the evap systems use a solenoid valve (this one may be hung open).

Something else you can check, since it looks fairly easy to remove the TB, You could take the bit you used to groove the TB and check your groove to make sure it is full depth throughout the groove.

What I mean by full depth is that when you put the bit in the groove, the shank directly behind the cutting surface of the bit should be making contact with the TB wall. If that is not the case then the groove pocket isn't at the correct depth to be effective.

Things that make you go... hmmmm

Karl Fortner
Tacoma, Washington

cut a groove in top also use med bit

Ask Dan about the ECU reset procedure on the Prius. He is "The Man" when it comes to these exotic hybrids...

Thanks guys.

I've checked for vacuum leaks and the groove is my best yet (out of the two that I've done). I've now capped the PCV inlet and will vent the hose into the air filter and do an ECU reset again.

Some further research and reading on Toyota and Prius forums, reveals that the 12V battery disconnect, does reset the Long Term Fuel Trims. It also revealed that, the fuel economy is usually worse, immediately after a reset and it takes around three weeks of regular driving, before the new trims are established.

I'll keep posting results and pictures as I have them.

Resetting ecu does 0 fuel trims on prius I have 4 of them 05 09 10 and 11 they all reset by un plugging batt overnight andleave head light switch on.

Did you groove top also as I said and how close did you groove to the butterfly?
This is very important as to location as the prius is a different bird.

The closer to butterfly the better as the engine is on and off so frequently. Its best to use a scanner to get best tps setting. If it doesnt run like a small v8 then your to far from butterfly!!!!!!!!!!!!!!!!!

The ecu will start to train tps setting fairly quick,the mpg will rise slowly you will learn to drive with the groove,remember this is a different bird.

Good luck my friend and happy grooving as it sounds as your on your way also dont always depend on the mpg gauge when grooving as they sometimes fool you check at pumps for true results.

Dan gadgetman mo.

I realised today that the picture that I included in my first post, wasn't displaying properly, so I've edited that post and here's a close up version. It's only about 1mm from the throttle plate. Today I'll remove it again, groove the top, plumb the PCV into the air intake and do another ECU reset.

Thanks Dan,

I've been busy with other things for a few weeks and now I have an opportunity to do some more work on the Prius. I'd like to clarify a few things first.

1. Grooving the top of the TB. Do I just continue the groove around? Do I stay 1mm off the throttle plate?

2. The Evaporative Control System connects at the back of the TB and the inlet is just after the plate. What should I do with this inlet?

3. There are two connections for the PCV. One connection is before the throttle plate (high pressure side) and connects at the back of the TB. The second connection is after the throttle plate (low pressure side) and connects at the front of the TB. Should one or both be capped or redirected?


I tried to extract the plugs for re-gapping today, but I'll have to buy another tool to fit.

Hi Will!

First off, the low pressure side is after the throttle plate. That is the line that needs be capped. Cap on both sides for max effect, leaving the other line alone.

As to the 'second groove', I suggest you use one groove, as instructed, until you've completed the process. Test that, then cut the other. This goes on the entry side, and is usually more difficult to do considering the depth of the TB.

Let me know how it goes!

There are two inlets on the low pressure side of the throttle plate. The inlet that is just after the groove, is the feed from the evaporative control system and is controlled by a solenoid valve. The second inlet on the low pressure side, is the return from the PCV.

First I capped the PCV inlet and there were no gains.
Then I capped the EVAP inlet and again there was no difference.

I've attached an image of the Prius throttle body, showing the view from the low pressure side. The red arrow is pointing to the PCV return and the inlet pipe pointing towards the camera, is the EVAP inlet, just after the groove. These are the ones that I have capped.

I'm determined to get this running like a small V8