sticky this, very important.

 

Thank you very much for the help.

I will take my Harrier to the garage these two days for the cleansing, and will let you guys know the result.

 

I'll stick it as I suppose that over time we will add other ideas.

 

After cleaning all the things mentioned, my gas mileage is still very bad, like 4.6km / L.

So, today my garage hooked the diagonise computer and discovered one of the three O2 sensor has 0 Volt, which means .... dead....

So, planning to get it changed next week.

I think O2 sensor affect the gas mileage, right?

 

It sure does affect gas mileage. We get a lot of blown sensors on vehicles down here, most people don't know until emissions time or when they realize they are wasting too much gas. A Renault Clio my company owns kept not being driven because people claimed it was wasting too much gas. My uncle serviced it and realized it had a bad A/F sensor and then one week later a bad ignition coil.

 

Oh yeah !~
My RX300 is now wasting too much gas right now...

 

4.6km/L is 11 MPG. Normal is 17 MPG.
Does your car jerk at high speeds but low RPMs?

Check out these two threads:
https://www.clublexus.com/forums/sho...d.php?t=288374
https://www.clublexus.com/forums/sho...d.php?t=295986

 

What does it mean by "jerk at high speed"?

My car always keep low RPM in highway ... Gear 3 always below 2000 rpm on street roads.

 

Just read the articles ...

No, my car doesn't jerk at high speed.

 

I have just sent the car to the garage again this afternoon the O2 sensor replacement. Let's see if the gas mileage can be improved after the service.

 

The O2 sensor hasn't been changed yesterday since my garage man cannot take out the sensor behind the Cat. However, there is a sign that the car has black exhaust ... Is it a sign for incomplete fuel burn ??

 

Where are you seeing the black exhaust?

In addition, which cat are you referring to, there should be two precats off of the manifold and 1 cat underneath the vehicle. The O2 sensor after the main cat underneath the vehicle isn't the key for the gas mileage, that would be the two A/F sensors before the precats.

 

Okay, finally my car has entered Toyota's (Lexus) garage today and the technician told me that the air mass is doubled more than normal. The reading on my car right now is 5.x and the norm is 2.x. That's why my car is now sucking fuel. He suggested me to change the MAF (which is next the air box) first to see if anything can be improved. He also told me that two O2 sensors in front (not the one behind the cat underneath the vehicle) have "Freezed" since the reading from MAF has exceeded the O2 sensors' handling ability. He hopes that after changing the MAF can make those two O2 sensors work again.

One more question, does your fusebox feel hot after a 40 min ride?
Many thanks.

 

One more thing, my garage man has swapped his MAF sensor from his Echo to mine. Still no changes. Is the MAF sensor on Echo different from mine? They look really the same.

 

Yes, they have different resistances. You don't really get a benefit from changing even to a different MAF sensor unless you are going to do some boosting. A lot of dudes over at Solaraguy.org throw Supra TT MAF Sensors when they are going to use a turbo.

Normally, the fusebox is hot because the hot engine contributes to that.

With my air intake modifications, I sometimes get an exceedingly high idle (which is great when this luckily occurs at the track, such as the time I clocked my record 17.931), but otherwise a nuisance.

The one thing that comes to mind right now is that the spark plugs may have some fouling and as such the combustion doesn't have as much efficacy, thus lower gas mileage. A Check Engine Light wouldn't necessarily pop up in this case. If you were here in Mexico, I could run a gas analysis test to see your HC (hydrocarbon or unburnt fuel count) and verify this better. Has your mechanic looked at any of the plugs.

The only other source of a higher volume of air without touching off a Check Engine Light is the area around the airbox where the air filter is kept and over time it can develop warpage and near the seams there are areas where extra air can seep in. Additionally, some air can seep in through cracks on one or both exhaust manifolds just before the A/F sensors.

I would make absolutely sure that MAF sensor is clean and that it is not missing and of the two threads inside the sensor itself as I showed in the picture on the other page. A dirty sensor is just going to let air pass in and it won't be properly recorded.