[rangerbentman]

I read the high fuel consumption thread and it said to start another . So here is another.
There did not seem to be an answer as to how to get decent mileage above 12.1 mpg my new to me van gets in combined city highway driving. Max speed up here is 100km / 62 mph where I am and as high as 70 further away. 136000 miles on odometer, no CEL yet and someone stated the O2 sensor on front and AF sensor on front being changed even though no codes are shown. On my sidekick I was having idle issues and I got the O2 sensor changed and for the most part the sidekick idles like it used to. There were no check engine lights on at all and for the Sienna idle is fine ,no odors, just paltry gas mileage ?

So anyone else have similar horrible gas mileage and found a cure?

 

[circus]

An inexpensive obd2 scanner allowed me to monitor the short and long term fuel trim on my 99. The control box thought the engine was running lean so it was adding fuel trying to compensate. A lot of fuel. Then it was just a matter of figuring out why the control box thought it was running lean. In my case it was a faulty mass air flow meter.

 

[BillG]

Yeah, you definitely need more data. You can do some preliminary checks like changing the air filter and inspect vacuum lines, but you need to know if it's rich or lean. Then, you narrow down the potential causes and eliminate some things entirely. OR just take it to a trustworthy mechanic and they'll do the same.

 

[rangerbentman]

My trusty mechanic will do the checks next wednesday as I have no electronic knowledge and very limited tools . Odd that the older I get the less strength in my hands , there must be kryptonite around here. Now I will find a how to video on sparkplug changing on the V6 , I hear three of them are a piece of cake ! I will keep you apprised of the findings and hopefully get decent mpg's

 

[3Wheelerguy]

I am going to say this. AWD Siennas are not known for making good fuel mileage.... Things that could make a difference. A clean air filter Air filter. Tire pressures also make a difference. I run 45PSI in mine.
Location/ area makes a difference also... Hills ETC.

 

[rangerbentman]

I am going to say this. AWD Siennas are not known for making good fuel mileage.... Things that could make a difference. A clean air filter Air filter. Tire pressures also make a difference. I run 45PSI in mine.
Location/ area makes a difference also... Hills ETC.

Yes I am aware that the awd does not get stellar mileage but when it gets less than advertised and I am not racing around , then something is amiss with the fuel mileage.

 

[circus]

My trusty mechanic will do the checks next wednesday as I have no electronic knowledge and very limited tools . Odd that the older I get the less strength in my hands

It's not knowledge, tools or strength, it's a question of stingy. I'm too stingy to pay a mechanic $150 for five minutes of scanning. Enjoy solving the mystery and once solved you'll be empowered from then on.
Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime.

 

[rangerbentman]

Good to see I am not the only cheap guy here! My mechanic does not charge for scanning , and his wife enjoys my cookies.
Give a man a fish and you feed him for a day; teach a man to fish and you find a taxation revenue stream.

 

[BillG]

FWIW, scanning is trivial. You don't pay for the 15-minute once-over and scan. You pay for the 15 years of experience it took to get to the point where you trust him to do the scanning.

Also, the secret to getting weaker as you get older is to use a longer pipe on the wrench.

 

[circus]

It took less than 300 miles in fuel saved to pay for the scanner. Maybe 600 miles for the time learning what the numbers and graphs meant. Next time, or different vehicle, it's free.
Only cure for weakness is use, mental or physical. Fix you car, you'll live longer.

 

[rangerbentman]

That overhead display that tells me what direction I am going and the gas mileage , is bouncing from 78 mpg ( I like that ) and down to 9.9 mpg?
So where is it getting it's information from?

 

[sixto]

Displayed mpg is generally based on wheel speed and injector pulse width over time.

Sixto
‘04 LE FWD

 

[rangerbentman]

Displayed mpg is generally based on wheel speed and injector pulse width over time.

Sixto
‘04 LE FWD

So I am doing 60 mph down the highway and the overhead display is constantly changing up to 78 mpg , down to 12 mpg , up again ? No drop in speed just steady .speed and wacko readings. Is this indicative of some sensor going awry? My MPG is about 12.6 when I hit the gas station and check mileage against gallons.

 

[sixto]

If you’re on level terrain with no change in rpm or load then that is strange. It was already suggested to check live data - MAF, fuel trims, throttle position, etc. I have a $15 Bluetooth dongle that works with my phone that shows live data.

Sixto
‘04 LE FWD 203K miles

 

[3Wheelerguy]

Weird.
OK. So try doing a manual MPG test. Seems you are only going off the data from the vehicle? Might be giving you bad info as it spikes up and down.
Run a tank or two to confirm what the Sienna is actually getting and don't worry about what the data is saying.

 

[Roader]

Seems you are only going off the data from the vehicle?

No:

My MPG is about 12.6 when I hit the gas station and check mileage against gallons.

 

[rangerbentman]

Unfortunately the last three fill ups or shall I say the first three as I have only had this from Nov 03/22 it has been consistent at 12.3 mpg combined city highway with more highway than city. So it is going to my mechanic, to have his far better tools diagnose and fix the mileage problem . I have no history of the van mechanical fixin's and I just saw that the sparkplugs are good for 120000 miles and the odometer says 134000 miles on the van . So just like my 98 Sidekick , things do need changing after a while. On the Sidekick 420000 km was the time when 3500.00 per year replacements started kicking in.

 

[circus]

So just like my 98 Sidekick , things do need changing after a while. On the Sidekick 420000 km was the time when 3500.00 per year replacements started kicking in.

Your over reacting. My former gas hog cost me $33 to fix. Including a new tire stem, the $35.00 per year replacements started kicking in. $33 scanner not included.

 

[rangerbentman]

I will post here what the Mechanic finds and does to get me better mileage . 420,000 km is 260,000 miles and my odometer says 134,000 so it has a ways to go before major fixing comes into the conversation.

 

[BillG]

I will post here what the Mechanic finds and does to get me better mileage . 420,000 km is 260,000 miles and my odometer says 134,000 so it has a ways to go before major fixing comes into the conversation.

FWIW, if the work is done at a mechanic, as it comes up, I would expect somewhere around $4-6k worth of work to be done over the span between 100k and 150k miles. Spark plugs, intake/TB gaskets, timing belt/water pump on the 3.3L or just the water pump on the 3.5L, radiator, front/rear suspension, brake work, O2/A-F sensors, exhaust, trans filter/flush, valve cover gaskets, etc. If you put off some stuff (i.e. suspension, exhaust, etc.) which doesn't particularly prevent you from driving the vehicle, I could see a large bill coming due every 6 months. If you take it to a dealer, that $4-6k would probably transform into $10-12k around here.