Hello,

So, while I was working on a DIY gasket change job on my 3GRFE 3L little beasty, I've discovered that I can actually see the intake valves (having the manifold air tank removed by default).


intake valves, 3GRFE

So I sneaked and captures couple of photos.
My question is are these valves considered dirty? Would cleaning them enhance performance? Especially that I am getting a lower mileage than one or two years ago?

I would appreciate "tested" thoughts about whether I need to clean them and what causes such a performance drop.

I think the same question is valid for all 2nd Gen IS engines(?)

 

The deposits on the runners is not ideal but I don't see that as your smoking gun for mpg loss. The valves themselves although dark and very mild buildup are pretty OK for intake valves.

You address the usual suspects?
MAF cleaning
Plugs
Tire pressure
Aged engine oil can be a factor too
Fuel quality

Those come to mind.

 

Yup done all of that.

> Tire pressure is good. (35 front, 38 rear).
> Oil is good (synthetic 5W30).
> Plugs checked and are good (and changed anyway)!
> MAF cleaned.
> Throttle body cleaned (engine RPM became better on D, before it dropped to 5 before coming back to 6.5)
> Fuel grade is 98 octane.

Can wheel alignment be the problem? Although the car drives perfectly straight!

 

Look at the tires edges. If feathered inside or out, the toe may be off.

 

You driving in ect mode? What the mpg?

 

I used to get 40 mpg (@74.5 mile/hour, flat road, AC on). Currently I am getting 33-35 mpg same conditions!
With a full tank I used to get above 310 miles, now I am getting around 250!
I turn the ECT on from time to time. How would ECT affect mileage (?)

 

I'd be happy w a solid 26. I get 21 to 23. 350 though! Never heard of any IS getting 30+. I'd go by miles traveled and gas pumped.

That said, it has 17 gal tank and my light comes on with 3.0 gallons left. A typical fuel up is 14 gallons and 300 to 340 miles traveled.
300mi/14 gal = 21.4mpg

Something doesn't add up for your case.

 

Hmmm, you are absolutely right. The tank mpg is less than that.
I just gave the value under specific condition: driving on a flat road non stop for one hour, speed fixed at 74.56 (120km/h) the reading used to be 40.35 mpg. And now it is less than that........

I think it is hard to compare different engine sizes, let alone the effect of oil grade, fuel type, road nature, AC or not, wheel size and pressure, wind condition, damn even altitude can affect mpg.

Just wanted to find out common issues with 2nd GEN IS's that cause increased fuel consumption .......