ilanh

I have year 2000 Harrier Four (RX300 AWD) 64,000km, fuel consumption is 4.0 km/l (around 10mpg), this seems to me way too high. It used to be 5.5 km/l before my mechanic cleaned the IAC - any idea??

Lexmex

Welcome to the Club. I've moved your post from the bad gas mileage thread to here.

When did you start noticing it was 10 mpg, was this recent?

sktn77a

iTrader: (2)

I take it by "Harrier Four" you mean the four cylinder engine? You should be getting WAY better gas mileage than 5.5km/L with only 40000 miles on it (you should reasonably expect around 10 in the 6 cylinder and better in the 4).

Something's not right - your mechanic aggravated the problem but didn't cause it.

ilanh

The problem started back in May 2009 after the car maintanence. I complained about un-stable/low idle speed so the mechanic removed the IACV (by removing the entire trotle body) and cleaned it.

Since then the consumption get worst, from 5.5 km/l to 4.0 km/l. I don't think 5.5 km/l is good at all but now it is worst.The idle RPM is mostly stable but sometimes it get un-stable and the engine even suddenly increase RMP at idle.

This is a year 2000 3.0 liter V6 Harrier with AWD. It has 65,000 km and mostly drive in city.

BTW - how often need to change the spark plugs?

sktn77a

iTrader: (2)

OK, "Four" stands for "Four Wheel Drive".

Your car came with iridium plugs - they should last 120,000 miles. Have they been changed previously to the wrong kind of plug, do you think? In any event, you should take the car to a Lexus or Toyota dealer to find out what the problem is. Most "mechanics" these days don't have the diagnostic equipment or experience to deal with complex fuel, ignition and computer systems.

Lexmex

Have you gotten any check engine lights since this whole thing started and if so what were they (I've got a hunch I know), but curious?

In addition, what kind of gasoline are you using (octane)?

ilanh

1. No check engine lamp turn on ever ( 2+ year since I own the car)
2. Using 95 unleaded fuel

updated informaton:
Yesterday I did the following action and the km/l indication on the LCD dash display jumped from 4.0 to 5.6 km/l (~13 mpg):

1. Cleaned the IACV only by removing the motor (black plastic part)
2. Cleaned the IACV conatct, the midlle contact was rusty (green rust) and also tigten the contacts
3. Cleaned the MAF
4. Adjust the trotlle position (by the screw on the bottom of the black half sphere where the accelerator cable connected), the screw was fully closed so released it 3~4 turns so now the screw is in a mid position.

After reseting the km/l meter the average fuel consumption jumped to 5.6 km/l and stayed there.

RE: item 4 above: I think this is the chock trotlle position adjustment (not sure), how to adjust this propoerly?

RE: fuel consumption @ 5.6 km/l (~13 mpg): is it normal, or should I keep looking for the reason for the high consumption?

sktn77a

iTrader: (2)

No this is not normal - you should be getting 18-22mpg per US gallon (more per Imperial gallon). Are you relying on an on-board computer estimate of mpg? If so, fill up the tank and do a manual estimate to see if they are the same. Have you had a compression check? 13mpg is terrible for a V6 RX300, unless you drive at the red line all the time!

ilanh

I did the real check with filling the tank and found the computer read is accurate so i trust the computer read.

What do you mean by "compression check"?

Lexmex

Simply stated you want to see the pressure in each of your cylinders. A competent mechanic should be able to do this. Over time, the cylinder walls can get pits or scratches and/or your piston rings/seals can go bad. It can be a combination of these issues.

For the cylinder walls, I use a product called Restore, http://www.restoreusa.com/Engine_Restorer.html (that was available when I lived in Mexico, but there are a lot of competitors and I am sure they have something similar where you live).

For the piston rings/seals, you can try Liqui Moly Motor Oil Saver. There is a distributor in Hong Kong,

RAIMI INTERNATIONAL LIMITED FLAT/A,G/F.,YUEN LONG HI-TECH CENTRE
NO.11 **** YIP ST.WEST
HK-00000 YUEN LONG,N.T. HONG KONG
Tel: 00852 2944 5600
Fax: 00852 2443 2398
E-Mail: raimi88hk@yahoo.com.hk

In addition, ask them if they have the Jectron fuel additive.

ilanh

Sound like my engine needs ovehoule!! I don't think this is the case since no oil consumption and no abnormal sound. Also the car drives great just take toouch gas

Lexmex

Check your tire pressure, too.

sktn77a

iTrader: (2)

I don't think engine wear requiring an overhaul is the most likely cause here. If you have a Lexus or Toyota dealer close by, I would take it in for a checkup - might be money well spent!

ilanh

Talking about tires, 6 month ago (together with the iac cleaning) I changed tires. I am using now 205/70 before it was 215/60. Air pressure using 30 psi. Could that be a reason?

Lexmex

Possibly part of it, what is the max psi rating you have on the side of your tires?