ScottAllen

Hi All,

I'm new to the forum and have enjoyed alot off the information here. This may be a dumb question, but I recently changed my plugs from copper to platinum. I gapped at the Scion recommended .032. The car runs great, but the gas mileage took a nosedive. I seem to recall the reference book at the parts store saying something about an .044 gap. Should platinum plugs be gapped differently than copper and should it be .044? Thanks much!

swartzautoman

iTrader: (3)

i still have less then 15k on my box so i haven done much thinking about what kind of plugs to use when i change them.

but..... this is a great question for all those who have changed the plugs already.

what type of plug did you use?
what did you gap them at?
what changes did you see in your gas milage?

XbbbbBox

I have changed plugs on my 05 xb twice. - I do once a year - around 30,000 - 35,000 miles. I found best plug for the money is NGK G Power Platinum #7090 - $9.68 at RockAuto.com for 4. Recomended gap is .32. Go by what manufacture says. Always right on out of the box.
Mileage increase is not noticable. Though he first time I replaced the plugs they were quite worn - much more than I had seen with any other vehicle.

ScottAllen

I installed Autolite Platinums. I've checked around on the web a bit too and still seeing the gap is supposed to be .044. That just seemed to be a huge difference when the previous was .032. I'll regap this weekend and see what happens. The stock plugs didn't look that bad with 50K on them.

jif

The general theory is you should run as wide a gap as your ignition can support (ie depends on coils, plugs, boost etc). This induces a stronger spark which is better at igniting cold/rich/lean mixtures

The NGK website recommends a 1.1mm (0.044") gap plug (BKR5EYA-11) FWIW. This should be in the owner's manual... which I don't have

ScottAllen

Thanks jif. I regapped to .044 this past weekend. It still smells like it is running rich. The jury is still out on the gas mileage. Maybe I should have taken the neg. battery cable off and reset the system? I will give that a try tonight.

Scorpius01

How many miles do you have on your Box? do you have an intake of some sort?

ScottAllen

51K for the mileage and a drop in K&N at the moment.

Scorpius01

Do you clean your Mass Airflow on a regular basis, K & N filters get Mass Airflow dirty really quick.
That would be a better explaination on poor fuel economy as that effects fuel delivery. spark plugs will have a minimal if any effect on fuel economy (not noticable).

ScottAllen

Nope, never ever have cleaned a MAS. Can you post a little instruction? I'm sure it is simple, but I don't want to miss or screw something up! I wouldn't think a replacement filter would make the MAS any dirtier than usual. BTW, the power reset did help.

Scorpius01

With the car off, unplug the Mass Airflow.
there will be two screws holding this sensor in.
unscrew them.
Gently pull the sensor out of the intake.
Get a flashlight. shine it into the sensor so you can see the Airflow and intake temp wire.
get an electronics cleaner and spay it on the two wire elements until clean. blow on it after cleaning to dry it faster.
now place it in the intake where you removed it from, put it in straight, and gently push on it until it seats.
put the two screws back in.
plug in the sensor.
The computer will already start learning to refuel the car within a couple of miles. No need to reset the computer, the processor in your car is incrediblely fast.

The oil from the K & N is what gets the MAF dirty.

jif

I kinda think a dirty MAF would register less air (=less fuel) ..?

Have you checked the usual suspects, tire pressure, o2 sensor, dirty air filter, CEL codes?

tCtCtC

dude wtf stop posting this ish everywhere

jetblast

Dont' forget the cooler temps of fall/winter will also cause your mileage to fall.

Scorpius01

It depends how dirty it is.
Lets explore what happens with a dirty MAF and what condition it creates.
A MAF sensor has two heated elements in it, one if for airflow calculation, the other element is for Intake air temp.
The passing air flows past these elements cooling them, this cooling creates a certain voltage based upon how cool it gets, which indicates air flow.
When these elements get dirty there are two conditions that can happen. A rich condition or a lean condition.
How dirty the element is depends on what code it could trip.

There are two codes for running conditions:
P0171 engine running lean; This actually creates a rich condition, the reason being is once the longterm fuel trim value has reached 25% +or-, the computer can no longer compensate, which would be the short term fuel trim. A P0171 will be expressed in a -25% on the longterm fuel trim. The short term fuel trim will start throwing in as much fuel as it can to try and balance this lean condition out up until 25%+ or -. With a reduced airflow reading from a dirty MAF and a short term value not being able to compensate we really have a rich condition, not enough air too much fuel.

P0172 engine running rich code; We have just the opposite of the mentioned code above. We really have a lean condition. The MAF has to get exceptionally dirty to throw this code. Long term fuel trim 25% Short term cannot compensate.

So what is a fuel trim do you ask? A Fuel trim is expressed in a percentage value against the fuel program in the ECM. For instance, -15% is that value off the program. So it is subtracting 15% fuel from the fuel program. A normal fuel trim value is 5% + or -. So if we had a Long term fuel trim value of 10% you would see a short term fuel trim value of (-5%)-(-8%).

There are two types of fuel trim values. Long term fuel trim indicates the actual condition or problem, the short term fuel trim indicates the computer correction.

OC_ScionBox

hey about Denso Iridium??

i think they're like $12 each one at Autozone
are they really worth it???